TW202218178A - Nitride semiconductor ultraviolet light emitting element - Google Patents

Abstract

This nitride semiconductor ultraviolet light emitting element comprises a light-emitting element structure unit in which an n-type layer composed of an AlGaN-based semiconductor having a wurtzite structure, an active layer, and p-type layers are stacked in an up-down direction. Each semiconductor layer is an epitaxially grown layer having a surface with multi-step terraces formed thereon that are parallel to a (0001) surface. The n-type layer has uniformly distributed layer-shaped regions that have a locally low AlN mole fraction, and n-type body regions that are other regions than the layer-shaped regions). A Ga-enriched n-type region including an n-type AlGaN region having an AlGaN composition ratio of AlnGa12-nN12 (n = 5, 6, 7, or 8) is present within the layer-shaped regions. An Al-enriched n-type region that has a locally high AlN mole fraction and that includes an n-type AlGaN region having an AlGaN composition ratio of Aln+1Ga11-nN12 is present within the n-type body regions. The n-type layer has an average AlN mole fraction Xna within the range of (n + 0.5)/12 < Xna < (n + 1)/12. Extending directions of the layer-shaped regions (21a) each have a portion inclined relative to an upper surface of the n-type layer.

Description

Nitride semiconductor ultraviolet light-emitting element

The present invention relates to a nitride semiconductor ultraviolet light emitting element formed of an AlGaN-based semiconductor having a sphalerite structure, an n-type layer, an active layer, and a p-type layer, which are laminated on a light-emitting element structure portion in the vertical direction.

Generally speaking, there are many nitride semiconductor light-emitting elements that are formed by epitaxial growth on a substrate such as sapphire to form a plurality of nitride semiconductor layers to form a light-emitting element structure. The nitride semiconductor layer is represented by the general formula Al _1-xy Ga _x In _y N (0≦x≦1,0≦y≦1,0≦x+y≦1).

The light-emitting element structure of the light-emitting diode is between the two cladding layers of the n-type nitride semiconductor layer and the p-type nitride semiconductor layer, and has a double-heterostructure in which an active layer formed through the nitride semiconductor layer is sandwiched. When the active layer is an AlGaN-based semiconductor, by adjusting the AlN molar ratio (also called the Al composition ratio), the bandgap energy is adjusted to the bandgap energy obtained by combining GaN and AlN (about 3.4eV and about 6.2eV). eV) is within the range of the lower limit and the upper limit, respectively, and an ultraviolet light emitting element with an emission wavelength of about 200 nm to about 365 nm can be obtained. Specifically, by flowing a forward current from the p-type nitride semiconductor layer toward the n-type nitride semiconductor layer, in the active layer, the recombination of carriers (electrons and holes) is generated, which corresponds to the above-mentioned energy band gap energy. glow. Since the forward current is supplied from the outside, a p-electrode is provided on the p-type nitride semiconductor layer, and an n-electrode is provided on the n-type nitride semiconductor layer.

When the active layer is an AlGaN-based semiconductor, the n-type nitride semiconductor layer and the p-type nitride semiconductor layer sandwiching the active layer are composed of an AlGaN-based semiconductor having a higher molar fraction of AlN than the active layer. However, since it is difficult to form a good ohmic contact with the p-electrode in a p-type nitride semiconductor layer with a high AlN molar ratio, it is generally formed on the uppermost layer of the p-type nitride semiconductor layer, which is compatible with a low AlN molar ratio. The p-type connection layer with good ohmic contact to the p-electrode is made of p-type AlGaN-based semiconductor (specifically, p-GaN). The p-type junction layer is made of AlN with a smaller molar fraction than the AlGaN-based semiconductor constituting the active layer, and the ultraviolet rays emitted from the active layer toward the p-type nitride semiconductor layer are absorbed in the p-type junction layer and cannot be effectively Take out to the outside of the element. For this reason, the general ultraviolet light-emitting diode system in which the active layer is an AlGaN-based semiconductor adopts the schematic display device structure shown in Fig. 22, and the ultraviolet light emitted from the active layer toward the n-type nitride semiconductor layer side can be effectively extracted to the outside of the device (for example, Refer to the following Patent Documents 1 and 2, etc.).

As shown in FIG. 22, a general ultraviolet light emitting diode system is deposited on a substrate 100 such as a sapphire substrate, and on a template 102 formed by depositing an AlGaN-based semiconductor layer 101 (for example, an AlN layer), an n-type AlGaN-based semiconductor layer 103, The active layer 104, the p-type AlGaN-based semiconductor layer 105, and the p-type connection layer 106, the active layer 104, the p-type AlGaN-based semiconductor layer 105, and a part of the p-type connection layer 106 until the n-type AlGaN-based semiconductor layer 103 is exposed Etching is performed to remove the n-type AlGaN-based semiconductor layer 103 on the exposed surface, the n-electrode 107 is formed on the surface of the p-type connection layer 106, and the p-electrode 108 is formed respectively.

In addition, in order to improve the luminous efficiency (internal quantum efficiency) formed by the recombination of carriers in the active layer, the active layer is formed into a multiple quantum well structure, and an electron barrier layer is provided on the active layer.

On the other hand, it has been reported that in the cladding layer composed of the n-type AlGaN-based semiconductor layer, the composition modulation caused by Ga segregation (segregation accompanying the mass shift of Ga) occurs, and the surface of the cladding layer extends in the syncline direction. Partially, a layered area with a low AlN molar ratio is formed (for example, refer to the following Patent Document 3, Non-Patent Documents 1 and 2, etc.). Since the band gap energy of the AlGaN-based semiconductor layer with a low AlN molar fraction is also locally reduced, it is reported in Patent Document 3 that the carriers in the cladding layer are easily localized in the layered region. , can provide a low-impedance current path for the active layer, and can achieve the improvement of the luminous efficiency of the ultraviolet light emitting diode. The above-mentioned characteristics of the layered field are also reflected in the high-angle annular dark field (HAADF)-STEM image from the n-type cladding layer of the conventional nitride semiconductor ultraviolet light-emitting element to the semiconductor layer of the electron barrier layer shown in FIG. 23 . confirm. The HAADF-STEM image can obtain ratio-to-atomic weight comparisons, and heavy elements are shown brightly. Therefore, the areas where the AlN molar ratio is low are displayed relatively brightly. The HAADF-STEM image is more suitable for the observation of the difference in AlN molar fraction than the usual STEM image (bright field image). [Prior Art Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2014/178288 [Patent Document 2] International Publication No. 2016/157518 [Patent Document 3] International Publication No. 2019/159265 [Non-patent literature]

[Non-Patent Literature 1] Y. Nagasawa, et al., "Comparison of Al _x Ga _1−x N multiple quantum wells designed for 265 and 285nm deep-ultraviolet LEDs grown on AlN templates having macrosteps", Applied Physics Express 12, 064009 (2019) [Non-Patent Literature 2] K. Kojima, et al., "Carrier localization structure combined with current micropaths in AlGaN quantum wells grown on an AlN template with macrosteps", Applied Physics letter 114, 011102 (2019)

[The problem to be solved by the invention]

The ultraviolet light-emitting element made of AlGaN-based semiconductor is fabricated on a substrate such as a sapphire substrate, for example, by a well-known epitaxial growth method such as an organometallic compound vapor deposition (MOVPE) method. However, when producing an ultraviolet light emitting element, the characteristics of the ultraviolet light emitting element (emission wavelength, socket efficiency, forward bias, etc.) are affected by the drift of the crystal growth device, so stable production is not necessarily easy. rate to be produced.

The drift of the crystal growth device is caused by the attachment of the carrier plate or the wall of the processing chamber, etc., which is caused by changing the effective temperature of the crystal growth site. For this reason, in order to suppress drift, the growth history has been reviewed in the past. Although experienced persons have made efforts such as subtly changing the set temperature or the composition of the raw material gas, or fixing the growth history for a certain period of time, maintenance such as cleaning is also carried out for a certain period of time. , but it is still difficult to completely rule out drift.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a nitride semiconductor ultraviolet light emitting device that can perform stable production with suppressed boating fluctuations due to drift of a crystal growth apparatus. [Means for solving problems]

In order to achieve the above object, the present invention provides a nitride semiconductor ultraviolet light-emitting element in which an n-type layer, an active layer, and a p-type layer formed of an AlGaN-based semiconductor having a sphalerite structure are stacked on a light-emitting element structure portion in the vertical direction. Among them, the n-type layer is composed of an n-type AlGaN-based semiconductor, and the active layer disposed between the n-type layer and the p-type layer has a well layer including one or more well layers composed of an AlGaN-based semiconductor. In the quantum well structure, the p-type layer is composed of p-type AlGaN-based semiconductor, the n-type layer, the active layer, and each semiconductor layer in the p-type layer have a multi-segment platform parallel to the (0001) plane. On the surface of the epitaxial growth layer, each semiconductor layer in the active layer has an inclined region that is inclined with respect to the (0001) plane between adjacent platforms connecting the multi-segmented platforms, and a platform region other than the aforementioned inclined region. , the aforementioned n-type layer has a layered domain with a low molar fraction of local AlN equally dispersed in the aforementioned n-type layer, and an n-type bulk domain other than the aforementioned layered domain, and the upper surface of the aforementioned n-type layer. Each extending direction of the layered region on the orthogonal first plane has a portion inclined with respect to the intersection of the upper surface of the n-type layer and the first plane, and the integer n is 5, 6, 7, or 8. In the aforementioned layered domain, there is a Ga _- enriched _n -type domain including an n-type AlGaN domain where the composition ratio of AlGaN is an integer ratio of _AlnGa12 -nN12, and in the aforementioned n-type bulk domain, there is an AlGaN domain The composition ratio becomes the n-type AlGaN region of the integer ratio of Al _n+1 Ga _11-n N ₁₂ , the Al-rich n-type region with a high AlN molar fraction locally, the average AlN molar fraction of the aforementioned n-type layer In the range of (n+0.5)/12<Xna<(n+1)/12, in the range of the ratio Xna, in the inclination region of the well layer, the AlN molar ratio is locally higher than the plateau of the well layer. The AlN molar fraction of the field is low in the Ga-enriched well field, which is the nitride semiconductor ultraviolet light emitting device of the first feature.

However, although the AlGaN-based semiconductor is represented by the general formula Al _1-x Ga _x N (0≦x≦1), the energy of the bandgap in which the bandgap energy of GaN and AlN can be obtained is the lower limit and the upper limit, respectively. Within the range, impurities such as group 3 elements such as B and In or group 5 elements such as P may be contained in trace amounts. In addition, although the GaN-based semiconductor is basically a nitride semiconductor composed of Ga and N, impurities such as group 3 elements such as Al, B, and In, or group 5 elements such as P and the like may be contained in small amounts. In addition, although the AlN-based semiconductor is a nitride semiconductor basically composed of Al and N, impurities such as a Group 3 element such as Ga, B, and In, or a Group 5 element such as P and the like may be contained in a small amount. Therefore, in the present invention, the GaN-based semiconductor and the AlN-based semiconductor are each a part of the AlGaN-based semiconductor.

Furthermore, an n-type or p-type AlGaN-based semiconductor is an AlGaN-based semiconductor doped with Si or Mg as a donor or acceptor impurity. In the present invention, p-type and n-type AlGaN-based semiconductors that are not specified means undoped AlGaN-based semiconductors, but even undoped, they may contain trace amounts of donor or acceptor impurities to an unavoidable degree. In addition, the first plane is an imaginary plane extending parallel to the up-down direction in the n-type layer, which is not a boundary interface with an exposed surface or other semiconductor layers specifically formed during the manufacturing process of the n-type layer. Furthermore, in this specification, the AlGaN-based semiconductor layer, the GaN-based semiconductor layer, and the AlN-based semiconductor layer are semiconductor layers each composed of an AlGaN-based semiconductor, a GaN-based semiconductor, and an AlN-based semiconductor.

In the nitride semiconductor ultraviolet light emitting device according to the first feature, as described below, the AlGaN composition ratio described later using the Ga-rich n-type region and the Al-rich n-type region formed in the n-type layer, respectively, is an integer. Compared with quasi-stable AlGaN, it is possible to suppress fluctuations in characteristics due to drift of the crystal growth device, and it can be expected to stably produce nitride semiconductor ultraviolet light-emitting elements with desired light-emitting properties.

First, "quasi-stable AlGaN" in which the composition ratio of AlGaN is represented by a specific integer ratio will be described.

Usually, the crystalline state of the ternary mixed crystal system such as AlGaN is randomly mixed with Group 3 elements (Al and Ga), and it is described as approximate "random nonuniformity". However, since the common bonding radius of Al is different from the common bonding radius of Ga, in the crystal structure, the atomic arrangement of Al and Ga is more symmetrical, and generally has a stable structure.

The AlGaN-based semiconductor system of the sphalerite structure has two kinds of arrangement: random arrangement with or without symmetry and stable symmetrical arrangement. Here, at a certain ratio, it appears that the symmetrical arrangement becomes the dominant state. In "quasi-stable AlGaN" in which the composition ratio of AlGaN (the composition ratio of Al to Ga to N) described later is represented by a specific integer ratio, a periodic symmetrical arrangement structure of Al and Ga is found.

In this periodic symmetrical arrangement structure, the supply amount of Ga is only slightly increased for the crystal growth plane, and due to the high symmetry, it becomes a mixed crystal molar ratio with stable energy, which can prevent Ga that is prone to mass transfer. , extremely increases the proliferation of places. That is, by utilizing the properties of "quasi-stable AlGaN" in the Ga-enriched n-type region formed in the n-type layer, as an AlGaN-based semiconductor, even if the fluctuation of the mixed crystal molar ratio occurs due to drift of the crystal growth device, etc. , as will be described later, the variation of the mixed crystal molar ratio in the layered region that provides a low-impedance current path to the active layer can still be locally suppressed. As a result, stable carrier supply from the n-type layer to the active layer can be achieved, and fluctuations in device characteristics can be suppressed, and stable production of nitride semiconductor ultraviolet light-emitting elements exhibiting desired characteristics can be expected.

Next, the composition ratio of AlGaN in which Al and Ga are periodically symmetrically arranged in the (0001) plane will be described.

In FIG. 1, a schematic diagram of 1 unit cell (2 single atomic layers) is shown in the c-axis direction of AlGaN. In FIG. 1 , the white circles show the positions of the atoms (Al, Ga) of the group 3 elements, and the black circles show the positions of the atoms (N) of the group 5 elements.

In FIG. 1 , the position planes (A3 and B3 planes) of the Group 3 elements and the position planes (A5 planes and B5 planes) of the Group 5 elements shown in hexagons are parallel to the (0001) plane. Among the positions of the A3 face and the A5 face (collectively referred to as the A face), there are six positions at each vertex of the hexagon, and one position at the center of the hexagon. The same is true for the B3 plane and the B5 plane (collectively referred to as the B plane), and in FIG. 1 , only three positions existing in the hexagon of the B plane are shown. Each position of the A surface overlaps the c-axis direction, and each position of the B surface overlaps the c-axis direction. However, an atom (N) at one position on the B5 plane is an atom (Al, Ga) at three positions on the A3 face above the B5 face, and an atom at one position on the B3 face on the lower side of the B5 face. (Al, Ga) form a 4-coordinate bond, an atom (Al, Ga) at one position on the B3 plane is an atom (N) at one position on the B5 plane above the B3 plane, and an atom (N) on the lower side of the B3 plane Since the atoms (N) at the three positions of the A5 plane form a 4-coordinate bond, as shown in FIG. 1 , the positions of the A plane do not overlap with the positions of the B plane in the c-axis direction.

FIG. 2 is a plan view showing the positional relationship between the positions of the A surface and the B surface, as viewed from the c-axis direction. On the A and B sides, each of the six vertices of the hexagon is shared by the other two adjacent hexagons, and the position of the center is not shared with the other hexagons, so within one hexagon, substantially There are 3 atomic positions. Therefore, there are 6 positions of atoms (Al, Ga) of group 3 elements and 6 positions of atoms (N) of group 5 elements per unit cell. Therefore, as the composition ratio of AlGaN except that GaN and AlN are represented by an integer ratio, there are the following five cases. 1) Al ₁ Ga ₅ N ₆ , 2) Al ₂ Ga ₄ N ₆ (=Al ₁ Ga ₂ N ₃ ), 3) Al ₃ Ga ₃ N ₆ (=Al ₁ Ga ₁ N ₂ ), 4) Al ₄ Ga ₂ N ₆ (=Al ₂ Ga ₁ N ₃ ), 5) Al ₅ Ga ₁ N ₆ .

In FIG. 3, the A3 surface and the B3 surface of the group 3 element of the above-mentioned five combinations are shown schematically. Ga is shown with black circles, and Al is shown with white circles.

In the case of Al ₁ Ga ₅ N ₆ shown in Fig. 3(A), Ga is located at the 6 apex positions of the A3 face and 6 apex positions and 1 central position of the B3 face, and Ga is located at 1 central position of the A3 face. , the bits have Al.

In the case of Al ₁ Ga ₂ N ₃ shown in Fig. 3(B), Ga is located at the three vertex positions and one center position of the A3 plane and B3 plane, and the three vertex positions of the A3 plane and the B3 plane are located at the position of Ga. There is Al.

In the case of Al ₁ Ga ₁ N ₂ shown in Fig. 3(C), there are Ga at the three vertex positions and one central position of the A3 face and three vertex positions of the B3 face, and the positions of the three vertexes of the A3 face are Al is located at the three vertex positions and one center position of the B3 face.

In the case of Al ₂ Ga ₁ N ₃ shown in Fig. 3(D), Ga is located at the three vertex positions of the A3 and B3 surfaces, and Ga is located at the three vertex positions and one center position of the A3 and B3 surfaces. There is Al. This is equivalent to the positions of Al and Ga when replacing Al ₁ Ga ₂ N ₃ shown in FIG. 3(B).

In the case of Al ₅ Ga ₁ N ₆ shown in Fig. 3(E), Ga is located at one central position of the A3 plane, and there are 6 vertex positions of the A3 plane and 6 vertex positions and 1 central position of the B3 plane. , the bits have Al. This is equivalent to the positions of Al and Ga when replacing Al ₁ Ga ₅ N ₆ shown in FIG. 3(A).

In Figure 3(A)~(E), it can be seen that when other hexagons are imagined to move at any one center of the 6 vertices of the hexagon, the positions of the 6 vertices on the A3 plane have Al or Ga, and at the center position of the 3 vertices of the A3 face, there are Al or Ga equivalent, and at the central position of the A3 face, there are Al or Ga and the 3 vertices of the A3 face. Position, bit has Al or Ga equivalent. The same is true for the B3 side. In addition, in each figure of FIG.3(A), (C) and (E), you may replace A3 surface and B3 surface.

In each of FIGS. 3(A) to (E), the atomic arrangement of Al and Ga maintains symmetry regardless of whether it is the A3 plane or the B3 plane. Also, even if the center of the hexagon is shifted, the atomic arrangement of Al and Ga maintains symmetry.

Moreover, in the A3 plane and the B3 plane of Fig. 3(A)~(E), when the hexagonal position plane is repeatedly arranged in a honeycomb shape, in the direction parallel to the (0001) plane, for example in [11-20] Direction, [10-10] direction, when viewing each position, Al and Ga are periodically repeated in place, or either Al or Ga is continuously in place. Therefore, they are all atomic arrangements of periodic symmetry.

Here, the AlN molar ratio x1 (x1=1/6, 1/3, 1/2, 2/3, 5/6) corresponding to the AlGaN composition ratios of the above 1) to 5) is set to Al _x1 Ga _1-x1 N is referred to as "the first quasi-stable AlGaN" for the convenience of description. The first quasi-stable AlGaN system is that the atomic arrangement of Al and Ga becomes a periodic symmetrical arrangement, resulting in an energetically stable AlGaN.

Next, when the positional planes shown in the hexagon shown in FIG. 1 are expanded to a 2-unit unit cell (4 monoatomic layers), the positional planes of group 3 elements (A3 plane, B3 plane) and the position plane of group 5 elements (A5 plane) , B5 face), there are 2 respectively, for every 2 unit cells, there are 12 positions of atoms of group 3 elements (Al, Ga), and 12 positions of atoms of group 5 elements (N). Therefore, as the AlGaN composition ratio represented by the integer ratio of GaN and AlN, in addition to the above-mentioned AlGaN composition ratios 1) to 5), there are the following six combinations. 6) Al ₁ Ga ₁₁ N ₁₂ (=GaN+Al ₁ Ga ₅ N ₆ ), 7) Al ₃ Ga ₉ N ₁₂ (=Al ₁ Ga ₃ N ₄ =Al ₁ Ga ₅ N ₆ +Al ₁ Ga ₂ N ₃ ), 8) Al ₅ Ga ₇ N ₁₂ (=Al ₁ Ga ₂ N ₃ +Al ₁ Ga ₁ N ₂ ), 9) Al ₇ Ga ₅ N ₁₂ (=Al ₁ Ga ₁ N ₂ +Al ₂ Ga ₁ N ₃ ), 10) Al ₉ Ga ₃ N ₁₂ (=Al ₃ Ga ₁ N ₄ =Al ₂ Ga ₁ N ₃ +Al ₅ Ga ₁ N ₆ ), 11) Al ₁₁ Ga ₁ N ₁₂ (=Al ₅ Ga ₁ N ₆ ) +AlN).

However, the six AlGaN composition ratios of 6) to 11) are formed by combining the first quasi-stable AlGaN, GaN, and AlN in the first and subsequent AlGaN composition ratios, so the symmetry in the c-axis direction Although the stability of AlGaN is higher than that of the first quasi-stable AlGaN, the symmetry of the atomic arrangement of Al and Ga in the A3 plane and the B3 plane is the same as that of the first quasi-stable AlGaN, which is more random. The stability of AlGaN in the asymmetric alignment state is high. Here, the AlN molar ratio x2 (x2=1/12, 1/4, 5/12, 7/12, 3/4, 11/12) corresponding to the AlGaN composition ratios in 6) to 11) above The _{Alx2Ga1 -x2N} is referred to as "the second quasi-stable AlGaN" for the convenience of description. From the above, the first and second quasi-stable AlGaN systems have a more stable structure than the symmetry of the atomic arrangement of Al and Ga in the crystal structure. Hereinafter, the first and second quasi-stable AlGaN are collectively referred to as "quasi-stable AlGaN".

Here, the AlGaN composition ratio represented by the integer ratio of the 11 kinds of quasi-stable AlGaN of the above 1) to 11) is expressed as Al _n Ga _12-n N ₁₂ when the integer n (n=1 to 11) is used to generalize , the AlN molar ratio becomes n/12. The integer n is the even number of 1) to 5) is the first quasi-stable AlGaN, and the integer n is the odd number of 6) to 11) is the second quasi-stable AlGaN. However, the AlN molar ratio of AlnGa12 _- nN12 is _n / ₁₂ when expressed as a trade number, but when expressed as a percentage, a mantissa will be generated below the decimal point. Therefore, in the following, for the convenience of description, 1/12, 2/12 (=1/6), 4/12 (=1/3), 5/12, 7/12, 8/12 expressed in fractions (=2/3), 10/12 (=5/6), 11/12 8 AlN molar ratios are approximately expressed as 8.3%, 16.7%, 33.3%, 41.7%, 58.3%, 66.7%, 83.3%, 91.7%.

To grow AlGaN with a certain crystal quality, crystal growth needs to be performed at a high temperature of 1000°C or higher. However, Ga is located at the position of the crystal surface, and after the atoms arrive, it is assumed to be disturbed at 1000°C or higher. On the other hand, Al-based, unlike Ga, is easily adsorbed to the surface, and the movement after entering the position is somewhat moved, but is strongly restricted.

Therefore, even if it is quasi-stable AlGaN, the molar ratio of Al ₁ Ga ₅ N ₆ in the above 1), Al ₁ Ga ₁₁ N ₁₂ in the above 6), and Al ₁ Ga ₃ N ₄ series AlN in the above 7) is all Below 25%, because the composition ratio of Ga is high, at the growth temperature around 1000°C, the movement of Ga is intense, the symmetry of the atomic arrangement is disordered, the atomic arrangement of Al and Ga is close to a random state, and the above-mentioned stability It is lower than other quasi-stable AlGaN.

Next, the "Ga-enriched n-type region" and the "Al-enriched n-type region" will be described. In the nitride semiconductor ultraviolet light emitting device of the above-mentioned first feature, each semiconductor layer in the n-type layer, the active layer, and the p-type layer has an epitaxial growth layer formed on the surface of the multi-segment platform parallel to the (0001) plane. Therefore, in the n-type layer, Ga, which is easy to mass transfer, moves on the platform of the n-type body region, and is concentrated in the boundary region between adjacent platforms, forming a region with a lower molar ratio than the AlN region of the n-type body region. The boundary region is accompanied by the epitaxial growth of the n-type AlGaN layer in the n-type layer, and extends obliquely upward for the (0001) plane, and the layered region with local low AlN molar ratio is formed in the same manner as dispersed in the n-type layer.

Here, with the mass shift of Ga from the n-type bulk domain to the layered domain, the AlN molar ratio in the layered domain decreases, and the mass shift amount of Ga in the layered domain (hereinafter, also referred to as Ga When the supply amount) is sufficiently large, a Ga _- rich _n -type region including n-type quasi-stable AlGaN whose composition ratio of AlGaN is _AlnGa12 -nN12 is formed in the layered region. The AlN molar ratio of the aforementioned quasi-stable AlGaN is close to the AlN molar ratio (n/12) which is lower than the average AlN molar ratio Xna of the n-type layer. In the Ga-enriched n-type region, by There is a quasi-stable AlGaN whose AlGaN composition ratio is _AlnGa12 -nN12, and the fluctuation of Ga supply in the Ga _- enriched _n -type region and the fluctuation of the average AlN molar ratio Xna are in this quasi-stable AlGaN is absorbed. That is, in the Ga-enriched n-type region, when the supply amount of Ga increases or the AlN molar ratio Xna decreases, the quasi-stable AlGaN increases and the Ga supply amount decreases, or when the AlN molar ratio Xna increases, the quasi-stable AlGaN increases is reduced, and as a result, the variation in the molar ratio of AlN in the Ga-enriched n-type region is suppressed.

In the general embodiment where the light emission from the well layer is extracted externally through the n-type layer, the AlN molar ratio in the Ga-enriched n-type region is generally higher than that in the Ga-enriched well region formed in the inclined region of the well layer. The molar ratio of AlN is set as high as 8.3% or more, preferably 16% or more. Therefore, by suppressing a significant drop in the molar ratio of AlN in the Ga-rich n-type region due to fluctuations in the Ga supply amount due to drift of the crystal growth device, it is possible to suppress light emission from the well layer in the Ga-rich well region absorbed, reducing the luminous efficiency.

On the other hand, arsenic, in the n-type bulk domain within the n-type layer, is adjacent to or near the edge of the layered domain within the n-type bulk domain by mass shifting Ga to the layered domain (hereinafter, the two are summarized). Simply referred to as "edge portion"), an Al-rich n-type domain with a higher AlN molar ratio than the average AlN molar ratio in the n-type bulk domain is formed. Here, the AlN molar ratio in the Al-rich n-type region increases in response to an increase in the Ga supply amount in the Ga-enriched n-type region or an increase in the AlN molar ratio Xna. Here, the Ga-enriched n-type domain is formed in a layered domain that is narrower than the n-type body domain in the n-type layer, or the mass transfer of Ga in the layered domain is caused by holding the layered domain. The reason why the n-type bulk domains on both sides are generated is based on the average AlN molar ratio Xna of the n-type layer, and the AlN in the n-type domain is enriched by Ga for the mass shift amount of Ga in the layered domain. The decrease in molar ratio is greater than the increase in AlN molar ratio in the Al-rich n-type domain.

Therefore, when the average AlN molar fraction Xna of the n-type layer is within an appropriate range of (n+0.5)/12<Xna<(n+1)/12, the supply amount of Ga in the layered region is sufficient. In the Ga _- enriched _n -type region, while forming quasi-stable AlGaN with a composition ratio of _AlnGa12 -nN12, in the Al-enriched n-type region, an AlGaN with a composition ratio of Aln ₊₁ is formed. Quasi-stable AlGaN of Ga _11-n N ₁₂ . In the Al-enriched n-type region, due to the presence of quasi-stable AlGaN with a composition ratio of Aln ₊₁ Ga _11-n N ₁₂ , the variation of the Ga supply in the Ga-enriched n-type region and the average Variations in the AlN molar fraction Xna are also absorbed in the quasi-stable AlGaN existing in the Al-rich n-type region. That is, in the Al-rich n-type region adjacent to the layered region in the n-type body region, there is an energetically stable quasi-stable AlGaN, which suppresses the transition from the n-type body region through the Al-rich n-type region in the layered region. The mass of the excess Ga is shifted, and the above-mentioned fluctuations in the supply of Ga can be suppressed from the sharp drop in the molar ratio of AlN in the Ga-enriched n-type region.

Here, as described above, in the n-type layer, a layered domain with a low AlN molar ratio is localized easily, and a low-impedance current path can be provided to the active layer. Also, in the active layer, in the Ga-rich well region with a low AlN molar ratio that exists locally in the inclined region of the well layer, the carriers are easily localized, and the inclined region of the well layer is located in the layer of the n-type layer. Because of the extension of the state domain, carriers can be efficiently supplied to the Ga-enriched well domain of the well layer through the layer domain. Therefore, by forming a quasi-stable AlGaN with AlGaN composition ratio of AlnGa12- _nN12 in the Ga _- enriched _n -type region of the layered region, and forming AlGaN in the Al-enriched n-type region of the n-type body region Quasi-stable AlGaN with a composition ratio of Al _n+1 Ga _11-n N ₁₂ , as the AlN molar ratio difference between the Ga-rich n-type region and the Al-rich n-type region, the stability is guaranteed to be 12 minutes 1 (about 8.33 %), which can more stably realize the provision of a low-impedance current path formed by the localization of the above-mentioned carriers. As a result, suppression of characteristic variation of the nitride semiconductor ultraviolet light emitting element can be achieved.

However, in the crystal growth of AlGaN, the state of random asymmetric arrangement and the state of regular symmetric arrangement are usually mixed, and the average AlN molar ratio Xna of the n-type layer is not within the above appropriate range. , in the range of n/12≦Xna≦(n+0.5)/12, when the supply of Ga is excessively increased, in the Ga _- enriched _n -type region, the composition ratio of AlGaN is formed as _AlnGa12 -nN12 While stabilizing AlGaN, non-quasi-stable AlGaN with random asymmetric arrangement of AlN molar ratio lower than n/12 can be formed. Furthermore, when the AlN molar fraction Xna is in the range of n/12≦Xna≦(n+0.5)/12, and the Ga supply amount is not sufficiently large, no AlGaN composition is formed in the Al-rich n-type region. For the quasi-stable AlGaN whose ratio is Al _n+1 Ga _{11 -n} N ₁₂ , the molar ratio of AlN in the Al-enriched n-type region also fluctuates with the fluctuation of the Ga supply.

Therefore, when the average AlN molar fraction Xna of the n-type layer is within the range of n/12≦Xna≦(n+0.5)/12, compared with (n+0.5)/12<Xna<( Within the range of n+1)/12, the difference in AlN molar ratio between the Ga-enriched n-type domain and the Al-enriched n-type domain will not become 1/12 of the stability (about 8.33%), and it is easy to fluctuate. Therefore, the degree of localization of carriers in the layered domain is reduced, and a situation in which the carriers expand from the layered domain to the n-type bulk domain occurs. Furthermore, when the random asymmetric arrangement of non-quasi-stable AlGaN with AlN molar ratio lower than n/12 is formed, the luminescence from the well layer is absorbed in the Ga-rich well region, resulting in a decrease in luminous efficiency. As a result, there is a possibility that the suppression of characteristic variation of the nitride semiconductor ultraviolet light emitting element cannot be sufficiently achieved.

More and `. In the nitride semiconductor ultraviolet light emitting element of the above-mentioned first feature, the average AlN molar fraction Xna of the n-type layer is preferably (n+0.9)/12 or less.

According to the above-mentioned suitable embodiment, in the Ga _- enriched _n -type region in the layered region, quasi-stable AlGaN with a composition ratio of _AlnGa12 -nN12 can be more stably formed, and the Al-rich region in the n-type body region can be formed more stably In the n-type field, quasi-stable AlGaN with the AlGaN composition ratio of Aln ₊ 1Ga11 _{- nN12} can be formed more stably.

Furthermore, the present invention provides that the p-type layer has, as the lowermost layer in the p-type layer, an electron barrier layer formed on the upper surface side of the uppermost layer of the one or more well layers, in addition to the above-mentioned first feature, The electron barrier layer respectively has an inclined region that is inclined to the (0001) plane between the adjacent platforms connecting the multi-segmented platforms, and a platform region other than the aforementioned inclined region. The integer m is 8, 9 or 10. In the aforementioned inclined region of the aforementioned electron barrier layer, there is a p-type AlGaN region including _{AlmGa12 - mN12} whose composition ratio of AlGaN is an integer ratio, a Ga-enriched EB region with a low AlN molar fraction locally, The nitride semiconductor ultraviolet light emitting element of the second feature is the average AlN molar fraction Xea of the electron barrier layer in the range of (m+0.24)/12≦Xea<(m+1)/12.

Here, the problem when the Ga-enriched EB region is not formed in the inclined region of the electron barrier layer will be described.

In order to achieve the improvement of luminous efficiency caused by the recombination of carriers (electrons and holes) in the well layer, it is necessary to efficiently perform implantation of carriers (electrons) from the n-type layer side in the well layer, and from Both of the implantation of carriers (holes) on the p-type layer side. Generally speaking, in order to improve the implantation efficiency of carriers (electrons) from the n-type layer to the well layer, the molar ratio of AlN is usually 80% higher than that of the n-type cladding layer or the quantum barrier layer. The electron barrier layer of AlN molar ratio is arranged on the p-type layer side of the active layer which is closest to the well layer of the p-type layer.

In the electron barrier layer, like the well layer, a multi-stage terrace parallel to the (0001) plane is formed, and an inclined region inclined with respect to the (0001) plane connecting adjacent terraces is formed. However, in general, since the molar fraction of AlN in the electron barrier layer is extremely high, the composition modulation caused by the segregation of Ga generated in the n-type cladding layer and the well layer is difficult to achieve in the electron barrier layer. Therefore, the molar ratio of AlN in the electron barrier layer is difficult to produce difference between the inclined domain and the plateau domain. As an example, in the HAADF-STEM of the conventional nitride semiconductor ultraviolet light-emitting device shown in FIG. 23, although it was confirmed that the composition modulation caused by the segregation of Ga in the n-type cladding layer and the well layer was generated, in the n-type cladding layer In the layered region and the inclined region of the well layer, the molar ratio of AlN decreases, but it cannot be confirmed that the composition modulation caused by the segregation of Ga in the electron barrier layer occurs. In the inclined region of the electron barrier layer, the A drop in AlN molar ratio.

And more. The film thickness of the sloping area of the well layer and the electron barrier layer is accompanied by the lateral growth of the side of the edge of the platform where the step flow grows. Because of the direction movement, the film thickness is thicker than that of the platform area other than the inclined area.

In the inclined region formed in the electron barrier layer, the composition modulation caused by the segregation of Ga does not occur, the situation such as the drop of the molar ratio of AlN locally in the well layer, and the situation where the film thickness is thicker than that of the plateau region, do not occur. It will become an obstacle to the effective implantation of carriers (holes) from the p-type layer to the well layer. This section will be explained schematically using FIG. 4 .

When a forward bias is applied between the p-electrode and the n-electrode, as shown schematically in Figure 4, although holes (h+) are implanted from the p-type junction layer (p-GaN) to the electron barrier layer (EB) ), as described above, in the electron barrier layer, the AlN molar ratio in the inclined region does not decrease locally, and does not stimulate the local existence of carriers (holes), on the contrary, the film thickness of the inclined region is thick , the resistance is high, which hinders the passage of holes. The holes implanted in the electron barrier layer reach the platform area in the well layer from the platform area. On the other hand, electrons (e-) pass through the layered region from the n-type cladding layer side and reach the inclined region in the well layer (QW). Electrons and holes are localized centers in the inclined field of the well layer (in the figure, represented by ☆ (star)) to emit light and recombine, and the holes that reach the platform field in the well layer need to diffuse to reach the inclined area. field. However, the diffusion length of holes is shorter than that of electrons, and the amount of holes that diffuse to the inclined domain is limited. The holes that reach the platform domain of the well layer are partly diffused in the platform domain, and the holes such as Al holes of point defects are diffused in the platform domain. Since the non-luminescent recombination center (in the figure, shown by ● (black circle)) is trapped and the non-luminescent recombination is performed, there is a problem that the internal quantum efficiency decreases.

In addition, in the nitride semiconductor ultraviolet light-emitting element with a peak emission wavelength of about 285 nm or more, compared with the case of less than about 285 nm, the AlGaN-based semiconductor constituting the well layer has a lower molar fraction of AlN than Al, which is a point defect. There are fewer holes, and the holes reaching the plateau region in the well layer are located in the plateau region with a higher AlN molar ratio than the inclined region, and the luminescence recombines, resulting in a problem of emitting light with a shorter wavelength than the oblique region. Specifically, in the emission spectrum, two emission peaks with different wavelengths are generated, and the two emission peaks of different wavelengths are not synthesized into a single peak, and the double-peak emission appears separately, which is a factor for decreasing the yield.

Therefore, in the nitride semiconductor ultraviolet light emitting device according to the second characteristic feature, in the inclined region of the electron barrier layer, there is a Ga-rich EB region where the AlN molar fraction is locally low, and in the Ga-rich EB region , can generate the localized existence of carriers (holes), as shown schematically in Figure 5, the holes (h+) implanted in the electron barrier layer (EB) are also directly implanted in the inclined area IA Inside. Then, it is directly implanted in the inclined area IA of the electronic barrier layer, in the non-diffusion platform area TA, and reaches the local existence center of the luminescence recombination in the inclined area IA of the well layer (QW) (in the figure marked with ☆ (star-shaped). ) as shown in the figure) increases significantly. As a result, directly implanted in the inclined area of the electron barrier layer, in the non-diffusion platform area, the amount of holes in the inclined area of the well layer that reaches the localized center of the light-emitting recombination is greatly increased, which can suppress the electron resistance. The decrease of the internal quantum efficiency and the generation of double emission peaks are caused when the Ga-enriched EB region is not formed in the inclined region of the barrier layer. However, the ● (black circle) in FIG. 5 is the same as in FIG. 4, showing the non-luminescent recombination center.

In the nitride semiconductor ultraviolet light emitting device according to the second feature, the quasi-stable AlGaN whose composition ratio of the Ga-rich EB region formed in the electron barrier layer is an integer ratio and the Ga-rich AlGaN in the n-type layer are used. In the n-type field, it is the same when forming quasi-stable AlGaN whose composition ratio of AlGaN is an integer ratio, suppressing characteristic variation due to drift of the crystal growth device, and stably producing nitride semiconductor ultraviolet light-emitting elements with desired light-emitting properties.

Furthermore, in the nitride semiconductor ultraviolet light-emitting device according to the second feature, the average AlN molar fraction Xea of the electron barrier layer is the relationship between (m+0.24)/12≦Xea<(m+1)/12 Therefore, the AlGaN composition ratio of AlmGa12- _mN12 ( _m =8~10) formed in the Ga _- rich EB field corresponds to the AlGaN composition ratio in the electron barrier layer, so that the plateau field and the Ga-rich EB are formed in the electronic barrier layer. The difference in AlN molar ratio between the fields is ensured to be more than about 2%, and the setting range of the AlN molar ratio in the platform field is adjusted. Therefore, the carriers (holes) in the p-type layer are more stably localized in the inclined domain of the Ga-enriched EB domain of the platform domain including the band gap energy of the platform domain in the electron barrier layer, which can be more stable and localized. In the electronic barrier layer, the current flows preferentially and stably into the Ga-enriched EB region, so as to suppress the characteristic variation of the nitride semiconductor ultraviolet light emitting device.

Furthermore, in addition to the above-mentioned second feature, in the present invention, there is an Al-enriched EB domain with a local high AlN molar fraction in the above-mentioned plateau domain of the above-mentioned electron barrier layer, and the integer m is 8 or 9. When the above-mentioned Al-enriched EB domain is a p-type AlGaN domain including Alm ₊ 1Ga11 _{- mN12} whose composition ratio is an integer ratio, the average AlN molar fraction Xea of the above-mentioned electron barrier layer is in (m The third characteristic is within the range of +0.5)/12<Xea<(m+1)/12.

In the nitride semiconductor ultraviolet light emitting device according to the third feature, the quasi-stable AlGaN in which the composition ratio of the AlGaN of the Ga-rich EB domain and the Al-rich EB domain formed in the electron barrier layer is an integer ratio is used, and the The Ga-enriched n-type region and the Al-enriched n-type region in the n-type layer are the same as when the quasi-stable AlGaN whose composition ratio of AlGaN is an integer ratio is formed, and the characteristic variation caused by the drift of the crystal growth device can be suppressed. The stable production of nitride semiconductor ultraviolet light-emitting elements with desired light-emitting properties is expected.

Furthermore, in the nitride semiconductor ultraviolet light emitting device of the second or third feature, the average AlN molar fraction Xea of the electron barrier layer is preferably (m+0.9)/12 or less.

According to the above-mentioned suitable embodiment, in the nitride semiconductor ultraviolet light emitting element of the second or third feature, in the Ga-rich EB region of the inclined region of the electron barrier layer, AlGaN can be more stably formed with a composition ratio of _Alm The quasi-stable AlGaN of Ga _12-m N ₁₂ , in the nitride semiconductor ultraviolet light-emitting element of the third feature, can be more stably formed in the Al-rich n-type region of the plateau region of the electron barrier layer, and the composition ratio is: Quasi-stable AlGaN of Al _m+1 Ga _11-m N ₁₂ .

Furthermore, the present invention provides a nitride semiconductor ultraviolet light-emitting element comprising an n-type layer, an active layer, and a p-type layer of an AlGaN-based semiconductor having a zinc blende structure, which are laminated on the light-emitting element structure portion in the vertical direction. The layer is composed of an n-type AlGaN-based semiconductor, and the active layer disposed between the n-type layer and the p-type layer has a quantum well structure including one or more well layers composed of the AlGaN-based semiconductor, and the above-mentioned The p-type layer is made of p-type AlGaN-based semiconductor, the n-type layer, the active layer, and the semiconductor layers in the p-type layer have epitaxial surfaces that form a multi-segment platform parallel to the (0001) plane. The growth layer, the semiconductor layers in the active layer and the electron barrier layer respectively have inclined regions that are inclined with respect to the (0001) plane between adjacent platforms connecting the multi-segment platforms, and platforms other than the inclined regions. The above-mentioned n-type layer has a localized AlN layered domain with a low molar fraction distributed uniformly in the above-mentioned n-type layer, and an n-type bulk domain other than the above-mentioned layered domain, and the above-mentioned n-type layer. Each extending direction of the layered region on a first plane orthogonal to the upper surface has a portion inclined with respect to the intersection of the upper surface of the n-type layer and the first plane, and the p-type layer has as the The lowermost layer in the p-type layer, the electron barrier layer formed on the upper surface side of the uppermost layer of the above-mentioned one or more well layers, the integer m is 8 or 9, and in the above-mentioned inclined area of the above-mentioned electron barrier layer, there are _The p-type AlGaN region where the AlGaN composition ratio is an integer ratio of AlmGa12 _{- mN12} , the Ga-rich EB region where the AlN molar fraction is locally low, and the plateau region of the electron barrier layer, exist The p-type AlGaN domain including Alm ₊ 1Ga11 _{- mN12} whose AlGaN composition ratio is an integer ratio, the Al-rich EB domain having a high AlN molar fraction locally, and the average AlN molar ratio of the aforementioned electron barrier layer The ear fraction Xea is within the range of (m+0.5)/12<Xea<(m+1)/12, and in the above-mentioned inclined region of the above-mentioned well layer, there is a higher locality of AlN molar rate than that of the above-mentioned well layer. The Ga-enriched well region with a low AlN molar fraction in the platform region is the nitride semiconductor ultraviolet light emitting device of the fourth feature.

According to the nitride semiconductor ultraviolet light emitting element according to the fourth feature, as in the nitride semiconductor ultraviolet light emitting element according to the second feature, in the slanted region of the electron barrier layer, there is Ga, which is locally low in AlN molar fraction. In the enriched EB field, in the Ga-enriched EB field, the localized existence of carriers (holes) can be generated, and the holes implanted in the electron barrier layer can also be directly implanted in the inclined field. As a result, directly implanted in the inclined area of the electron barrier layer, in the non-diffusion platform area, the amount of holes in the inclined area of the well layer that reaches the localized center of the light-emitting recombination is greatly increased, which can suppress the electron resistance. The decrease of the internal quantum efficiency and the generation of double emission peaks are caused when the Ga-enriched EB region is not formed in the inclined region of the barrier layer.

Furthermore, in the nitride semiconductor ultraviolet light emitting element according to the fourth feature, in the electron barrier layer, Ga-enriched EB regions are formed in the inclined regions by mass-shifting Ga to the inclined regions, and at the same time adjacent to the terraces. The edge of the sloping field is internalized to form an Al-rich EB field with a higher AlN molar ratio than the average AlN molar ratio in the plateau field. Then, using the quasi-stable AlGaN whose composition ratio of the Ga-rich EB domain and the Al-rich EB domain respectively formed in the electron barrier layer is an integer ratio, in the nitride semiconductor ultraviolet light emitting element of the above-mentioned first feature, In the same way as when the Ga-enriched n-type region and the Al-enriched n-type region in the n-type layer are respectively formed into quasi-stable AlGaN whose composition ratio is an integer ratio, it is possible to suppress characteristic variation due to drift of the crystal growth device, etc. Stable production of nitride semiconductor ultraviolet light-emitting elements with desired light-emitting properties can be expected.

Furthermore, in the nitride semiconductor ultraviolet light emitting device according to the fourth feature, the average AlN molar fraction Xea of the electron barrier layer is the equation of (m+0.5)/12<Xea<(m+1)/12 Therefore, within the appropriate range, when the supply amount of Ga in the inclined region is sufficiently large, in the Ga-rich EB region, quasi-stable AlGaN with a composition ratio of _{AlmGa12 - mN12} is formed, while the Al-rich AlGaN is formed. In the chemical EB field, quasi-stable AlGaN with a composition ratio of Aln ₊ 1Ga11 _{- nN12} is formed. In the field of Al-enriched EB, due to the presence of quasi-stable AlGaN with a composition ratio of Alm ₊₁ Ga _11-m N ₁₂ , the variation of Ga supply in the field of Ga-enriched EB, and the average AlN molar The variation in ear fraction Xea is also absorbed in the quasi-stable AlGaN present in the Al-rich EB domain. That is, by the presence of energy-stable quasi-stable AlGaN in the Al-rich EB region adjacent to the slanted region in the electron barrier layer, excess in the slanted region from the plateau region via the Al-rich EB region can be suppressed. The mass shift of Ga suppresses the significant drop in the molar ratio of AlN in the Ga-enriched EB area caused by the change in the supply amount of Ga.

Furthermore, in the nitride semiconductor ultraviolet light emitting device of the fourth feature, the average AlN molar fraction Xea of the electron barrier layer is preferably (m+0.9)/12 or less.

According to the above-mentioned suitable embodiment, in the Ga-enriched EB region of the inclined region of the electron barrier layer, quasi-stable AlGaN with a composition ratio of _{AlmGa12 - mN12} can be formed more stably in the region adjacent to the plateau region. In the Al-enriched EB region at the edge of the inclined region, quasi-stable AlGaN with the AlGaN composition ratio of Alm ₊ 1Ga11 _{- mN12} can be formed more stably.

Furthermore, in addition to the above-mentioned fourth feature, the present invention provides that when the integer n is 5, 6, 7, or 8, in the aforementioned layered region, there is _{AlnGa12 - nN12} including AlGaN whose composition ratio is an integer ratio. In the Ga-enriched n-type region of the n-type AlGaN region, the average AlN molar fraction Xna of the n-type layer is the fifth in the range of (n+0.24)/12<Xna<(n+1)/12 Characteristic nitride semiconductor ultraviolet light-emitting element.

According to the nitride semiconductor ultraviolet light-emitting element according to the fifth feature, as the mass of Ga moves from the n-type bulk region to the layered region, the molar ratio of AlN in the layered region decreases. When the mass shift amount of Ga is sufficiently large, a Ga _- enriched n-type region including an _n -type AlGaN region with AlGaN composition ratio of _AlnGa12 -nN12 is formed in the layered region. The AlN molar ratio of the aforementioned quasi-stable AlGaN is close to the AlN molar ratio (n/12) which is lower than the average AlN molar ratio Xna of the n-type layer. In the Ga-enriched n-type region, by There is a quasi-stable AlGaN whose AlGaN composition ratio is _AlnGa12 -nN12, and the fluctuation of Ga supply in the Ga _- enriched _n -type region and the fluctuation of the average AlN molar ratio Xna are in this quasi-stable AlGaN is absorbed. That is, in the Ga-enriched n-type region, when the supply amount of Ga increases or the AlN molar ratio Xna decreases, the quasi-stable AlGaN increases and the Ga supply amount decreases, or when the AlN molar ratio Xna increases, the quasi-stable AlGaN increases is reduced, and as a result, the variation in the molar ratio of AlN in the Ga-enriched n-type region is suppressed.

Furthermore, in the nitride semiconductor ultraviolet light emitting device according to the fifth feature, the average AlN molar fraction Xna of the n-type layer is in the range of (n+0.24)/12<Xna<(n+1)/12 Therefore, corresponding to the AlGaN composition ratio of AlnGa12- _nN12 ( _n =5~8) formed in the Ga _- enriched n-type region, in the n-type layer, the layered region and the n-type bulk region are formed. The difference in AlN molar ratio between them is ensured to be more than about 2%, and the setting range of the AlN molar ratio in the n-type body area is adjusted. Therefore, the carriers (electrons) in the n-type layer are localized in the n-type layer more stably and locally in the layered domain including the Ga-enriched n-type domain with a smaller energy bandgap energy than the n-type bulk domain. In the n-type layer, the current system can preferentially and stably flow into the Ga-enriched n-type region, so as to suppress the characteristic variation of the nitride semiconductor ultraviolet light-emitting element.

Furthermore, the present invention provides, in addition to the above-mentioned first to fifth features, that the active layer has a multiple quantum well structure including two or more of the well layers, and between the two well layers, there is a structure composed of an AlGaN-based semiconductor. The barrier layer is the nitride semiconductor ultraviolet light emitting element of the sixth feature.

According to the nitride semiconductor ultraviolet light emitting device of the sixth feature, the active layer has a multiple quantum well structure, and the well layer can be expected to improve the luminous efficiency compared to the case of only one layer.

Furthermore, in the nitride semiconductor ultraviolet light emitting device of the sixth feature, the barrier layer is formed of an AlGaN-based semiconductor, and each has a (0001) plane inclination with respect to the adjacent terraces connecting the multi-segment terraces. In the inclined area of the barrier layer, and the plateau area other than the inclined area, the AlN molar ratio in the inclined area of the barrier layer is locally lower than the AlN molar rate in the plateau area of the barrier layer. Ga enrichment barrier field is better.

Through the above-mentioned appropriate embodiments, in the barrier layer, similarly to the Ga-enriched n-type region of the n-type layer and the Ga-enriched well region of the well layer, carriers can be generated in the Ga-enriched barrier region localized existence. Therefore, when supplying carriers (electrons) from the n-type layer to the Ga-enriched well region in the inclined region between the adjacent terraces of the well layer emission concentration, the Ga-enriched n-type region of the n-type layer can be passed through. The Ga-enriched barrier area of the barrier layer is efficiently performed.

In the above-mentioned suitable embodiment of the nitride semiconductor ultraviolet light emitting device of the above-mentioned sixth feature, the integer j is 6, 7, 8, 9 or 10, and the Ga-enriched barrier region includes _Alj whose composition ratio of AlGaN becomes an integer ratio. In the AlGaN field of Ga _12-j N ₁₂ , it is more preferable that the average AlN molar fraction Xba of the barrier layer is in the range of (j+0.24)/12≦Xba<(j+1)/12.

By the above-mentioned suitable embodiment, the variation of the mixed crystal molar ratio caused by the drift of the crystal growth device, etc. is suppressed, and in the barrier layer, the inclined region of the localization of the carrier is generated, and the AlN corresponding to the integer j is used. The mole fraction is formed stably.

Furthermore, the nitride semiconductor ultraviolet light emitting element of any one of the first to sixth features further includes a base portion including a sapphire substrate, and the sapphire substrate is inclined only by a specific angle with respect to the (0001) plane. The main surface, above the main surface, the light-emitting element structure portion is formed, at least each semiconductor layer from the main surface of the sapphire substrate to the surface of the active layer has a multi-segment platform parallel to the (0001) plane. The epitaxial growth layer on the surface is better.

Through the above-mentioned suitable embodiments, a sapphire substrate with an off-angle can be used to perform epitaxial growth on the surface of each layer from the main surface of the sapphire substrate to the surface of the active layer in the form of a multi-segment platform to achieve the above Nitride semiconductor ultraviolet light-emitting element of each characteristic.

In the nitride semiconductor ultraviolet light emitting device according to any one of the first to sixth features, the integer k is 3, 4, 5, 6, or 7, and for the integer n, k≦n−1, and the aforementioned Ga-rich The chemical well region is preferably an AlGaN region including _{AlkGa12 - kN12} in which the composition ratio of AlGaN is an integer ratio.

By the above-mentioned suitable embodiment, the variation of the mixed crystal molar ratio caused by the drift of the crystal growth device, etc. is suppressed, and in the well layer, the inclined region of the localization of the carrier is generated, and the target corresponding to the peak emission wavelength is made. The AlN molar ratio of the integer k determined by the value is stably formed. [Inventive effect]

According to the nitride semiconductor ultraviolet light emitting element according to the above-mentioned feature, it is possible to stably provide a nitride semiconductor ultraviolet light emitting element having desired light emitting characteristics and suppressing characteristic variation due to drift or the like of the crystal growth device.

The nitride semiconductor ultraviolet light-emitting element (hereinafter, simply abbreviated as "light-emitting element") according to the embodiment of the present invention will be described with reference to the drawings. However, in the schematic drawings of the drawings used in the following description, in order to facilitate the understanding of the description, the main parts are emphasized and the content of the present invention is schematically shown, and the dimensions of each part are not necessarily the same as the actual components. Hereinafter, in this embodiment, the light-emitting element will be described as a light-emitting diode.

[1st Embodiment] <Element structure of light-emitting element> As shown in FIG. 6 , the light-emitting element 1 of the first embodiment includes a base material portion 10 including a sapphire substrate 11 , a plurality of AlGaN-based semiconductor layers 21 to 24 , and a light-emitting element structure portion including a p-electrode 26 and an n-electrode 27 . 20. The light-emitting element 1 is mounted (flip-chip mounting) with the light-emitting element structure portion 20 side (upper side in the drawing in FIG. 6 ) facing the mounting base (sub-mount, etc.), and the light extraction direction is the base portion 10 side ( The lower side of the figure in Figure 6). However, in this specification, for the convenience of description, the direction perpendicular to the main surface 11a of the sapphire substrate 11 (or the upper surface of the base material portion 10 and each of the AlGaN-based semiconductor layers 21 to 24 ) is referred to as the "up-down direction" ( or "longitudinal direction"), let the direction from the base material portion 10 toward the light-emitting element structure portion 20 be the upward direction, and the opposite direction is the downward direction. In addition, let the plane parallel to an up-down direction be called a "1st plane". Furthermore, the plane parallel to the main surface 11a of the sapphire substrate 11 (or the upper surface of the base material portion 10 and the respective AlGaN-based semiconductor layers 21 to 24 ) is referred to as a "second plane", and a plane parallel to the second plane is referred to as a "second plane". The direction is called "horizontal direction".

The base material portion 10 includes a sapphire substrate 11 and an AlN layer 12 formed directly on the main surface 11 a of the sapphire substrate 11 . The main surface 11a of the sapphire substrate 11 is inclined at an angle (off angle) within a certain range (eg, about 0 to 6 degrees) with respect to the (0001) plane, and the main surface 11a exhibits a multi-segment platform on the slightly inclined substrate.

The AlN layer 12 is composed of AlN crystal epitaxially grown from the main surface of the sapphire substrate 11 , and the AlN crystal system has an epitaxial crystal orientation relationship with respect to the main surface 11 a of the sapphire substrate 11 . Specifically, for example, the AlN crystal is grown so that the C-axis direction (<0001> direction) of the sapphire substrate 11 is aligned with the C-axis direction of the AlN crystal. However, the AlN crystal system constituting the AlN layer 12 may contain a small amount of Ga or other impurities, and may also be an AlN-based semiconductor layer. In the present embodiment, the thickness of the AlN layer 12 is assumed to be approximately 2 μm to 3 μm. However, the structure of the base material part 10, the substrate used, etc. are not limited to the above-mentioned structure. For example, between the AlN layer 12 and the AlGaN-based semiconductor layer 21 , an AlGaN-based semiconductor layer having an AlN molar fraction equal to or higher than the AlN molar fraction of the AlGaN-based semiconductor layer 21 may be provided.

The AlGaN-based semiconductor layers 21 to 24 of the light-emitting element structure portion 20 are provided with an n-type cladding layer 21 (n-type layer), an active layer 22 , and an electron barrier layer 23 (p-type layer) in this order from the base portion 10 side. ), a structure in which the p-type connection layer 24 (p-type layer) is sequentially epitaxially grown and laminated.

In the present embodiment, the AlN layer 12 of the base material portion 10 , the n-type cladding layer 21 of the light-emitting element structure portion 20 and the semiconductor layers in the active layer 22 are sequentially epitaxially grown from the main surface 11 a of the sapphire substrate 11 . The electron barrier layer 23 has a surface derived from the main surface 11 a of the sapphire substrate 11 to form a multi-segment platform parallel to the (0001) plane. However, for the p-type connection layer 24 of the p-type layer, formed on the electron barrier layer 23 by epitaxial growth, although the same multi-segmented platform can be formed, it may not have the same multi-segmented platform. the surface of the platform.

However, as shown in FIG. 6 , the active layer 22 , the electron barrier layer 23 , and the p-type connection layer 24 are stacked on the second region R2 above the n-type cladding layer 21 in the light-emitting element structure 20 . The other part is removed by etching or the like, and is formed on the first region R1 on the upper surface of the n-type cladding layer 21 . Then, the upper surface of the n-type cladding layer 21 is exposed in the second region R2 excluding the first region R1. The upper surface of the n-type cladding layer 21 is schematically shown in FIG. 6 . There is a difference in height between the first region R1 and the second region R2. At this time, the upper surface of the n-type cladding layer 21 is in the first region R1. It is specified separately from the second area R2.

The n-type cladding layer 21 is composed of an n-type AlGaN-based semiconductor, and in the n-type cladding layer 21 and in the n-type cladding layer 21, there are locally dispersed AlN layered regions 21a with a low molar ratio. . The layered region 21a is as described above in the section of the prior art, since the bandgap energy is locally reduced, the carriers are easily localized and operate as a low-impedance current path. In this layered region 21a, as described above, the _n -type AlGaN region containing AlnGa12 _- nN12 whose composition ratio is an integer ratio (that is, the AlN molar ratio of n/ ₁₂ ) is dominated. 12) The n-type quasi-stable AlGaN) Ga-enriched n-type field. However, in this embodiment, the integer n is 5, 6, 7, or 8. That is, _four types of _{n -} type quasi-stable AlGaN _- based _Al5Ga7N12 , _Al1Ga1N2 , _Al7Ga5N12 , and _Al2Ga1N3 contained in the Ga _- rich _{n -} type _region , AlN The molar ratios were 41.7% (5/12), 50% (1/2), 58.3% (7/12), and 66.7% (2/3). In FIG. 6 , as an example of the existence of a Ga-rich n-type domain that dominates the layered domain 21 a , the layered domain 21 a is a schematic illustration of a case where all of the layered domain 21 a becomes a Ga-rich n-type domain. The area other than the layered area 21a in the n-type cladding layer 21 is referred to as the n-type body area 21b.

Although not shown in FIG. 6, the inner system of the layered domain 21a including the Ga-enriched n-type domain is formed by mass transfer of Ga from the n-type body domain 21b. In the n-type body domain 21b, especially in the The edge portions on both sides of the layered domain 21a are sandwiched to form a localized Al-rich n-type domain with a high AlN molar ratio. Furthermore, in the present embodiment, in the Al-rich n-type region, there is an n-type AlGaN region in which the composition ratio of AlGaN is an integer ratio of Aln ₊ 1Ga11 _- nN12 (that is, the molar ratio of AlN is ₁₂ parts). The (n+1) n-type quasi-stable AlGaN). That is, the AlN molar ratio of n-type quasi-stable AlGaN existing in the Al-rich n-type region is 12 times higher than the AlN molar ratio of n-type quasi-stable AlGaN existing in the Ga-rich n-type region 1 (about 8.3%). In the following, for the sake of brevity, the n-type AlGaN domain _of quasi-stable AlGaN where the composition ratio of AlGaN existing in the Ga _- enriched _n -type domain is the integer ratio of AlnGa12-nN12 is referred to as the n-type AlGaN domain for convenience. The "first quasi-stable n-type region" is the n-type AlGaN region where the composition ratio of AlGaN existing in the Al-rich n-type region becomes the integer ratio of Aln ₊ 1Ga11 _{- nN12} , which is quasi-stable AlGaN. It is called the "Second Quasi-Stable N-Type Domain".

In the present embodiment, the average AlN molar fraction Xna of the n-type cladding layer 21 is adjusted to be within the first appropriate range of (n+0.5)/12<Xna<(n+1)/12, more preferably It is adjusted to be within the second appropriate range of (n+0.5)/12<Xna≦(n+0.9)/12.

The average AlN molar fraction Xna of the n-type cladding layer 21 is used as a target value of the AlN molar fraction when the n-type cladding layer 21 is formed as described later. In addition, the average AlN molar fraction Xna is formed in the multi-segment plateau formed in the film formation of the n-type cladding layer 21 and the boundary region connecting the plateaus is respectively included in plural numbers in a wide range in the lateral direction, for example It can be determined by composition analysis of Al and Ga in the n-type cladding layer 21 formed by Rutherford Backscattering (RBS) analysis. In the RBS analysis method, for example, a He ²⁺ ion beam (beam diameter: 2.2 mm) is irradiated vertically from the upper surface side of the n-type cladding layer 21 of the sample at an accelerating voltage of 2.3 MeV, but the measurement range in the vertical direction is as large as 300 nm. Therefore, the film thickness of the object to be analyzed needs to be larger than 300 nm. Therefore, for the semiconductor layers other than the n-type cladding layer 21 with a film thickness of less than 300 nm, the average AlN molar ratio is determined by energy dispersive X-ray spectroscopy (cross-sectional TEM-EDX), which will be described later, or CL (cathode). ray luminescence) method to obtain the average value of the AlN molar ratios measured in the area where the scores are complex.

As described above, with respect to the mass shift amount of Ga from the n-type bulk region 21b to the layered region 21a, the degree of decrease in the molar ratio of AlN in the Ga-enriched n-type region (let the average AlN molar The ratio Xna as a benchmark) is greater than the increase in the molar ratio of AlN in the Al-enriched n-type region. Therefore, as schematically shown in the left part of FIG. 7, by setting the AlN molar ratio Xna to be higher than the AlN molar ratio of the first quasi-stable n-type region in the Ga-enriched n-type region (Xn0=n/ 12) The average value ((n+0.5)/12) of the AlN molar ratio (Xn1=(n+1)/12) of the second quasi-stable n-type field of the Al-enriched n-type field is high, corresponding to In the Ga-rich n-type region and the Al-enriched n-type region, the mass shift amount of Ga can be respectively stable to form two types of quasi-stable n-type regions whose AlN molar ratios differ only by 1/12. Here, as schematically shown in the right part of FIG. 7, by setting the AlN molar ratio Xna to be lower than the above-mentioned average value ((n+0.5)/12), when the mass shift amount of Ga increases excessively, In the layered region 21a, in addition to the first quasi-stable n-type region with AlN molar ratio Xn0 (=n/12), non-quasi-stable AlGaN with low AlN molar ratio can be further formed. Furthermore, when the mass transfer amount of Ga is insufficient, the AlN molality in the Al-rich n-type region cannot reach the AlN molality Xn1 (=(n+1) in the second quasi-stable n-type region. /12).

The average AlN molar ratio of the n-type bulk domain 21b excluding the Al-enriched n-type domain is similar to the average AlN molar ratio Xna of the n-type cladding layer 21 . Therefore, the difference between the AlN molar ratio of the Ga-rich n-type domain in which the first quasi-stable n-type domain with AlN molar ratio of n/12 exists and the average AlN molar ratio of the n-type bulk domain 21b is governed by Because it is more than 1/24 (about 4.17%), the effect of localized existence of carriers can be stably exerted.

By forming the Ga-enriched n-type region and the Al-enriched n-type region with the first and second quasi-stable n-type regions with high stability, respectively, it is possible to suppress the mixed crystal molar ratio due to drift of the crystal growth device. In the n-type cladding layer 21, a Ga-rich n-type region where the localized presence of carriers is generated is stably added at the molar rate of AlN corresponding to the first quasi-stable n-type region used. form. As a result, in the n-type cladding layer 21 , the current flows preferentially and stably into the Ga-enriched n-type region, and it is possible to further suppress the characteristic variation of the light-emitting element 1 .

In the present embodiment, the film thickness of the n-type cladding layer 21 is the same as the film thickness used in general nitride semiconductor ultraviolet light emitting elements, and it is assumed to be 1 μm to 2 μm, but the film thickness may be about 2 μm to 4 μm. .

The layered area 21a of the n-type cladding layer 21 is shown in FIG. 6 , and one layer is shown in a doublet pattern, and a plurality of layers exist away from each other in the upward and downward directions. In addition, with a first plane parallel to the vertical direction (for example, the cross section shown in FIG. 6 ), the extending direction of at least a part of the layered area 21a is relative to the horizontal direction (the intersection of the first plane and the second plane). extending direction) becomes inclined. The above-mentioned features of the layered region 21a are also confirmed in the HAADF-STEM image of the n-type cladding layer of the conventional nitride semiconductor ultraviolet light emitting device shown in FIG. 23 .

However, on the first plane shown in FIG. 6, although each layer of the layered area 21a is shown as a pattern parallel line (double line), the inclination angle formed by the extending direction and the horizontal direction is tied to each layered area 21a. The time is not necessarily the same, and within the same layered area 21a, the layered area 21a on the first plane is not necessarily limited to extend in a straight line because the position may vary. In addition, this inclination angle changes with the orientation of a 1st plane. Therefore, a part of the layered area 21a is on the first plane, and may intersect with the other layered area 21a, or may diverge from the other layered area 21a.

In addition, the layered areas 21a are shown on the first plane in FIG. 6, and although they are respectively shown by one line (double line), in the direction perpendicular to the first plane, they extend parallel or obliquely to the second plane , with a 2-dimensional extension. Therefore, the plurality of layered regions 21a exist on the plurality of second planes in the n-type cladding layer 21 in a striped shape.

The layered region 21a is a region in which the molar ratio of AlN is locally low in the n-type cladding layer 21 as described above. That is, the AlN molar ratio of the layered region 21a is lower than the AlN molar ratio of the n-type bulk region 21b. Further, in the vicinity of the boundary between the layered domain 21a and the n-type bulk domain 21b, when the AlN molar ratios of the two domains are progressively continuous, the boundary between the two domains cannot be clearly defined.

The AlN molar ratio of the layered region 21a in the n-type cladding layer 21 is the AlN molar ratio (n/12) of the first quasi-stable n-type region in the Ga-rich n-type region, more specifically In other words, let the integer n be any one of 5, 6, 7, or 8, and as described later, it is set in accordance with the AlN molar ratio in the well layer 220, and the AlN molar ratio in the well layer 220 is The target value corresponding to the peak emission wavelength is set.

The active layer 22 is composed of multiple quantum layers including two or more well layers 220 composed of AlGaN-based semiconductors or GaN-based semiconductors and one or more barrier layers 221 composed of AlGaN-based semiconductors or AlN-based semiconductors alternately laminated. well structure. The barrier layer 221 need not necessarily be provided between the well layer 220 and the n-type cladding layer 21 in the lowermost layer. In addition, in this embodiment, as a preferred embodiment, although the barrier layer 221 is not provided between the uppermost well layer 220 and the electron barrier layer 23, as a preferred embodiment, the barrier layer 221 is provided as A thin film of AlN with a high molar fraction can also be used as an AlGaN layer or an AlN layer.

The electron barrier layer 23 is formed of a p-type AlGaN-based semiconductor. The p-type connection layer 24 is formed of a p-type AlGaN-based semiconductor or a p-type GaN-based semiconductor. The p-type connection layer 24 is typically formed of p-GaN.

In FIG. 8, an example of the laminated structure (multiple quantum well structure) of the well layer 220 of the active layer 22 and the barrier layer 221 is shown schematically. In FIG. 8 , a case where the well layer 220 is three layers and the barrier layer 221 is two layers is illustrated. The uppermost well layer 220 is located between the electron barrier layer 23 and the upper barrier layer 221, the middle well layer 220 is located between the upper and lower barrier layers 221, and the lowermost well layer 220 is located between the upper and lower barrier layers 221. Between the barrier layer 221 on the lower side and the n-type cladding layer 21 .

The structure in which the well layer 220, the barrier layer 221, and the mesa T of the electron barrier layer 23 shown in FIG. 8 are grown in multiple stages is a well-known structure as disclosed in the above-mentioned Non-Patent Documents 1 and 2. In each layer, as described above, between the terraces T adjacent to the lateral direction, the inclined area IA inclined with respect to the (0001) plane is formed. The area outside the inclined area IA that is held up and down by the platform T is called the platform area TA. In the present embodiment, the depth of one terrace T (the distance between adjacent inclined regions IA) is assumed to be several 10 nm to several 100 nm. Therefore, the stepped (0001) surface in the inclined area IA is distinguished from the terrace surface of the multi-segment terrace T.

As schematically shown in FIG. 8 , in the electron barrier layer 23 , in the inclined region IA, a Ga-enriched EB region 23 a with a lower AlN molar fraction than the plateau region TA is formed. The well layer 220 is made of AlGaN-based semiconductor, and when the AlN molar ratio is not 0%, in each layer of the well layer 220, in the inclined region IA, the AlN molar ratio is lower than that in the plateau region TA. A Ga-rich well region 220a. The barrier layer 221 is formed of an AlGaN-based semiconductor, and when the AlN molar ratio is not 100%, in each layer of the well layer 221, like the electron barrier layer 23 and the well layer 220, in the inclined region IA, it is formed. The Ga-enriched barrier area 221a having a lower AlN molar fraction is compared to the platform area TA. In each layer of the electron barrier layer 23, the well layer 220, and the barrier layer 221, through the mass movement of Ga from the plateau region TA to the tilt region IA, localized AlN molar ratios are formed in the respective tilt regions IA These are low Ga-enriched EB fields 23a, Ga-enriched well fields 220a, and Ga-enriched barrier fields 221a.

That is, in the n-type cladding layer 21, the carriers are easily localized in the layered region 21a where the AlN molar ratio is locally low, and in the active layer 22, in the localized region IA existing in the inclined region IA of the well layer 220 In the Ga-rich well region 220a with a low AlN molar ratio, and in the localized AlN low molar Ga-rich barrier region 221a in the inclined region IA where the barrier layer 221 exists, individual carriers are prone to In the electron barrier layer 23, in the localized AlN low molar Ga-rich EB region 23a existing in the inclined region IA, the carrier is carried in the localization. Therefore, the layered domain 21a is interposed from the n-type cladding layer 21 side, and the Ga-rich EB domain 23a is interposed from the electron barrier layer 23 side, and the Ga-rich well domain 220a of the well layer 220 can be respectively By supplying carriers efficiently, it becomes a device structure that can achieve the enhancement of luminous efficiency by the recombination of carriers (electrons and holes) in the well layer 220 .

Moreover, although not shown in FIG. 8, as a preferred embodiment, in the electronic barrier layer 23, at the edge portion of the platform area TA adjacent to the inclined area IA, the average AlN of the electronic barrier layer 23 is made. Using the molar fraction Xea as a benchmark, an Al-rich EB domain with a high local AlN molar fraction is formed.

Furthermore, although not shown in FIG. 8 , as a preferred embodiment, the barrier layer 221 is made of AlGaN-based semiconductor, and when the AlN molar ratio is not 100%, in each layer of the barrier layer 221 , the electron resistance is connected to the barrier layer 221 . The barrier layer 23 is the same. At the edge of the platform region TA adjacent to the inclined region IA, the average AlN molar ratio Xba of the barrier layer 221 is used as a reference to form an Al rich localized AlN molar ratio. Chemical barriers.

The average AlN molar fractions Xea and Xba of the electron barrier layer 23 and the barrier layer 221 are as described later, and are the targets of the AlN molar fractions when each of the electron barrier layer 23 and the barrier layer 221 is formed into a film. value is used.

In this embodiment, the film thickness of the electron barrier layer 23 includes the plateau area TA and the inclined area IA, and is set in the range of, for example, 15 nm to 30 nm (the optimum value is about 20 nm). The film thickness of the well layer 220 includes the plateau region TA and the inclined region IA, for example, within the range of 1.5 unit cells to 7 unit cells, and is set corresponding to the target value of the peak emission wavelength of the light-emitting element 1 . In addition, the film thickness of the barrier layer 221 includes the plateau area TA and the inclined area IA, and is set in the range of, for example, 6 nm˜8 nm.

The well layer 220 is made of AlGaN-based semiconductor, and when the AlN molar ratio is not 0%, the AlN molar ratio of the Ga-enriched well region 220a of the well layer 220 corresponds to the target of the peak emission wavelength of the light-emitting element 1 . value is set. As a preferred embodiment, in the Ga-enriched well region 220a of the well layer 220, a quasi-stable well region formed of AlGaN with an integer composition ratio of _{AlkGa12 - kN12} is formed. However, the integer k is 3, 4, 5, 6 or 7, and is determined according to the target value of the peak emission wavelength. That is, the quasi-stable well regions existing in the Ga-rich well region 220a are Al ₁ Ga ₃ N ₄ , Al ₁ Ga ₂ N ₃ , Al ₅ Ga ₇ N ₁₂ , Al ₁ Ga ₁ N ₂ , and Al ₇ Ga ₅ N ₁₂ Of the 5 types, the AlN molar ratios are 25% (1/4), 33.3% (1/3), 41.7% (5/12), 50% (1/2), 58.3 % (7/12). However, as an embodiment, although it is preferable that the quasi-stable well region exists in the Ga-rich well region 220a, the Ga-rich well region 220a includes AlN molar ratio as the difference between the quasi-stable well region and the well layer 220. The region of AlN molality in the middle of the AlN molality of the platform region TA may also be used, and in the relevant case, the localized existence of carriers occurs in the inclined region IA of the well layer 220 .

As a preferred embodiment of the above, the Ga-enriched well region 220a is constituted by a quasi-stable well region with high stability, and the Ga-enriched n-type region and the Al-enriched n-type region in the n-type cladding layer 21 are formed. The first and second quasi-stable n-type domains with high stability, respectively, have the effect of suppressing the variation of the molar ratio of mixed crystals due to drift of the crystal growth device, etc. in the well layer 220 . In the layer 220, the Ga-enriched well region 220a, which generates the localized existence of carriers, is stably formed at a molar ratio of AlN corresponding to the quasi-stable well region used. As a result, in the well layer 220 , the current flows preferentially and stably into the Ga-enriched well region, and furthermore, the characteristic variation of the light-emitting element 1 can be suppressed.

The well layer 220 is made of a GaN-based semiconductor. When the AlN molar fraction is 0%, the barrier layer, the electron barrier layer 23 and the AlN molar fraction of the n-type cladding layer 21 are adjacent to the well layer 220 . The rate and the film thickness of the well layer 220 are set according to the target value of the peak emission wavelength of the light-emitting element 1 .

FIGS. 9 , 10 and 11 are for the quantum well structure model in which the well layer 220 and the barrier layer 221 are composed of AlGaN, and the film thickness of the well layer ranges from 3ML (single atomic layer) to 14ML (1.5 unit crystal). The simulation results (equivalent to the peak emission wavelength) obtained by changing the emission wavelength within the range of 4ML to 14ML (2 to 7 unit cells). As a condition for the above simulation, in FIG. 9 , the AlN molar ratio in the Ga-enriched well region 220a of the well layer 220 is set to be 50% (1/2) of the AlN molar ratio in the quasi-stable well region. In 10, the AlN molar ratio of the well layer 220 is enriched with Ga in the well region 220a, and the AlN molar ratio of the quasi-stable well region is 41.7% (5/12). In FIG. 11, the AlN molar ratio of the well layer 220 The AlN molar ratio of the Ga-enriched well region 220a becomes 33.3% (1/3) of the AlN molar ratio in the quasi-stable well region. In each of FIG. 9 to FIG. 11 , the Ga The AlN molar ratio of the enrichment barrier area 221a is 66.7% (2/3), 75% (3/4), and 83.3% (5/6). In the simulation results shown in FIGS. 9 to 11 , it is assumed that the ultraviolet light emission of the well layer 220 occurs remarkably in the inclined region IA. For this reason, it is important that the film thickness condition of the well layer 220 satisfies the inclined region IA.

From FIGS. 9 to 11 , it can be seen that when the film thickness of the well layer 220 is in the range of 3ML to 14ML, the smaller the film thickness of the well layer 220 is, the greater the quantum confinement effect of the well layer 220 is, and the emission wavelength is shortened. Furthermore, the greater the molar ratio of AlN of the barrier layer 221 is, the greater the degree of variation of the emission wavelength is with respect to the variation of the film thickness of the well layer 220 . Also, as shown in FIG. 9, when the AlN molar ratio of the Ga-enriched well region 220a is 50%, within the above-mentioned ranges of the film thickness of the well layer 220 and the AlN molar ratio of the barrier layer 221, it can be seen that the emission wavelength is The range of 246nm~295nm is roughly changed. As shown in FIG. 10, when the AlN molar ratio of the Ga-enriched well region 220a is 41.7%, within the above ranges of the film thickness of the well layer 220 and the AlN molar ratio of the barrier layer 221, it can be seen that the emission wavelength is approximately 249 nm ~311nm range variation. As shown in FIG. 11 , when the AlN molar ratio of the Ga-enriched well region 220 a is 33.3%, within the above-mentioned ranges of the film thickness of the well layer 220 and the AlN molar ratio of the barrier layer 221 , it can be seen that the emission wavelength is approximately 261 nm. ~328nm range variation. Furthermore, when the barrier layer 221 is made of AlN (AlN molar ratio=100%), the emission wavelength can be further extended.

9 to 11, in the Ga-enriched well region 220a of the well layer 220, a quasi-stable well region with AlGaN composition ratio of Al ₁ Ga ₁ N ₂ or Al ₅ Ga ₇ N ₁₂ or Al ₁ Ga ₂ N ₃ is formed, Corresponding to the AlN molar ratio of the quasi-stable well region, the film thickness of the well layer 220 is adjusted in the range of 3ML~14ML, and the Ga enrichment of the barrier layer 221 is made to enrich the AlN molar ratio of the barrier region 221a. The rate is adjusted within the range of 66.7%~100%, and the peak emission wavelength can be set within the range of 246nm~328nm by adjusting individually.

Figure 12 The well layer is GaN. For the quantum well structure model in which the barrier layer is composed of AlGaN or AlN, the molar ratio of AlN to the barrier layer is 66.7% (AlGaN) and 100% (AlN). In this case, the simulation results of the emission wavelength (equivalent to the peak emission wavelength) obtained by changing the film thickness of the well layer in the range of 4ML to 10ML are graphed. From FIG. 12 , within this range, it can be seen that the emission wavelength changes in a range of approximately 270 nm to 325 nm. Therefore, even when the well layer is composed of GaN (AlN molar ratio = 0%), the thickness of the well layer 220 is adjusted in the range of 4ML-10ML, and the barrier region 221a of the barrier layer 221 is enriched with Ga. The AlN molar ratio is adjusted in the range of 66.7%~100%, so that the peak emission wavelength can be set in the range of 270nm~325nm.

Through FIG. 12 , when the target value of the peak emission wavelength is in the range of 270 nm to 325 nm, as the composition ratio of AlGaN in the quasi-stable well region formed in the Ga-enriched well region 220 a of the well layer 220 , except those shown in FIGS. 9 to 11 . In addition to Al ₁ Ga ₁ N ₂ , Al ₅ Ga ₇ N ₁₂ , and Al ₁ Ga ₂ N ₃ , Al ₁ Ga ₃ N ₄ (AlN molar ratio of 25% (1/4)), or , Al ₁ Ga ₅ N ₆ (AlN molar ratio of 16.7% (1/6)). At this time, since the molar ratio of AlN in the quasi-stable well region is decreased from 33.3% to 8.33% (1/12), the molar ratio of AlN in the barrier layer 221 is also suitable for the peak emission wavelength. Within the range of the target value, it can be set lower than 66.7%, for example, it can be set at 58.3% or 50%.

Furthermore, as shown in FIGS. 9 to 11 , the composition ratio of AlGaN in the quasi-stable well region is Al ₇ Ga ₅ except for Al ₁ Ga ₁ N ₂ , Al ₅ Ga ₇ N ₁₂ , and Al ₁ Ga ₂ N ₃ . At N ₁₂ , the corresponding AlN molar ratio is only about 8.33% higher, and the peak emission wavelength is shortened to a longer wavelength. Therefore, when the target value of the peak emission wavelength is, for example, shorter than 250 nm, the composition ratio of AlGaN in the quasi-stable well region formed in the Ga-rich well region 220a can also be set to Al ₇ Ga ₅ N ₁₂ (mol fraction of AlN rate was 58.3% (12 out of 7)).

In addition, the well layer 220 is made of an AlGaN-based semiconductor, and when the AlN molar ratio is not 0%, the average AlN molar ratio Xwa of the well layer 220 is taken as an example, and AlN molar is formed in the Ga-enriched well region 220a. When the ear fraction Xw0 is in the quasi-stable trap area, it is better to roughly adjust it in the range of Xw0+2%~Xw0+3%. Through this preferred embodiment, the AlN molar ratio difference between the quasi-stable well region and the plateau region TA of the well layer 220 becomes a double emission peak that can suppress the AlN molar ratio difference caused by the tilt region IA and the plateau region TA. less than 4% of the production. However, even if the AlN molar ratio Xwa in the plateau region of the well layer 220 exceeds the range of Xw0+2%~Xw0+3%, only in the inclined region IA of the well layer 220, a localized AlN molar ratio is formed When the Ga-rich well region 220a has a low rate, the molar ratio of AlN in the Ga-rich well region 220a corresponding to the target value of the peak emission wavelength can be set to Xw1%, which is set at Xw1+2%~Xw1+3 Any value within the range of %.

The average AlN molar ratio Xwa of the well layer 220 is used as a target value of the AlN molar ratio when the well layer 220 is formed as described later.

The AlN molar ratio of the layered region 21a of the n-type cladding layer 21 is higher than the AlN molar ratio of the Ga-enriched well region 220a of the well layer 220, and is set to 8.3% or more, preferably 16% or more. at a high level.

As a preferred embodiment, in the Ga-enriched well region 220a of the well layer 220, a quasi-stable well region of AlkGa12 _{-kN12 ( k} =3˜7) whose composition ratio of AlGaN is an integer ratio dominates, In the layered region 21a in the n-type cladding layer 21, when the first quasi-stable n-type region in which the composition ratio of AlGaN becomes an integer ratio of AlnGa12 _{-nN12 ( n} =5~8) is dominant, The possible combination between the AlGaN composition ratio in the quasi-stable well region and the AlGaN composition ratio in the first quasi-stable n-type region is the combination of n≧k+1, which can satisfy the above conditions (layered region 21a and Ga enrichment). The AlN molar ratio difference of the well region 220a is 8.3% or more). Therefore, in the above preferred embodiment, the possible combinations of integer k and integer n are (k=3~4:n=5~8), (k=5:n=6~8), (k=6 :n=7~8), (k=7:n=8).

The AlN molar ratio of the Ga-enriched barrier region 221a of the barrier layer 221 is as described above, corresponding to the target value of the peak emission wavelength of the light-emitting element 1, along with the AlN molar ratio of the Ga-enriched well region 220a of the well layer 220. The ear fraction and the film thickness of the well layer 220 are, for example, adjusted within the range of 50% to 100%. Furthermore, as a preferred embodiment, when the barrier layer 221 is made of AlGaN-based semiconductor (excluding AlN-based semiconductor), the Ga-enriched barrier region 221a of the barrier layer 221 is formed with an AlGaN composition ratio that is an integer ratio. The quasi-stable barrier field formed by the quasi-stable AlGaN of Al _j Ga _12-j N ₁₂ . However, the integer j is 6, 7, 8, 9 or 10, which is determined according to the target value of the peak emission wavelength. That is, the quasi-stable barrier regions existing in the Ga-enriched barrier region 221a are Al ₁ Ga ₁ N ₂ , Al ₇ Ga ₅ N ₁₂ , Al ₂ Ga ₁ N ₃ , Al ₃ Ga ₁ N ₄ , and Al ₅ Ga ₁ N ₆ of the 5 types, AlN molar ratios are 50% (1/2), 58.3% (7/12), 66.7% (2/3), 75% (3/4) ), 83.3% (5 out of 6).

In addition, when the barrier layer 221 is made of AlGaN-based semiconductor (excluding AlN-based semiconductor), the molar ratio of AlN in the plateau region TA of the barrier layer 221 is about 51%-90%, which is richer than Ga The AlN molar ratio of the chemical barrier region 221a is set to be 1% or more, preferably 2% or more, more preferably 4% or more, and set at a high level. In order to fully ensure the localization effect of carriers in the Ga-enriched barrier region 221a, although the difference in AlN molar ratio between the Ga-enriched barrier region 221a in the barrier layer 221 and the platform region TA is set to be 4~5% The above is better, but at the level of 1~2%, the localized effect of the carrier can be expected.

In the Ga-enriched barrier region 221a of the barrier layer 221, the above-mentioned AlGaN composition ratio (Al _j Ga _12-j N ₁₂ , j=6~10) is formed, and the AlN molar ratio is Xb0 (=j/12) When the barrier layer is quasi-stabilized, the average AlN molar fraction Xba of the barrier layer 221 is preferably adjusted within the range of (j+0.24)/12≦Xba<(j+1)/12. The average AlN molar ratio of the platform area TA of the barrier layer 221 (when the Al-enriched barrier area is not formed, the Al-rich barrier area is excluded) is the average AlN molar ratio of the barrier layer 221 Xba is similar. Therefore, the difference in molar ratio between the Ga-enriched barrier region 221a of the barrier layer 221 and the AlN molar ratio of the platform region TA can be guaranteed to be more than about 2%. More preferably, the upper limit of the adjustment range of AlN molar ratio Xba is reduced from (j+1)/12 to (j+0.9)/12, and the composition ratio of AlGaN formed in the Ga-enriched barrier region 221a is more stable to be Al The quasi-stable barrier field of _j Ga _12-j N ₁₂ .

Furthermore, the average AlN molar fraction Xba of the barrier layer 221 is adjusted to be within the first appropriate range of (j+0.5)/12<Xba<(j+1)/12, more preferably ( It is better to be within the second appropriate range of j+0.5)/12<Xba≦(j+0.9)/12. Therefore, in the Ga-enriched barrier region 221a, the formation of non-quasi-stable AlGaN with a lower molar ratio of AlN than the quasi-stable barrier region of AlN molar ratio of Xb0 (=j/12) is suppressed, which is more stable A specific AlN molar difference between the well layer 220 and the barrier layer 221 of the inclined area IA is ensured.

However, even if the average AlN molar fraction Xba of the barrier layer 221 exceeds the range of (j+0.24)/12≦Xba<(j+1)/12, as long as it is formed in the inclined area IA of the barrier layer 221 The Ga-enriched barrier region 221a that can localize the carriers can obtain any molar ratio of AlN in the Ga-enriched well region 220a corresponding to the well layer 220 in the range of about 51% to 90%. value.

As a preferred embodiment of the above, the Ga-enriched barrier region 221a is formed as a quasi-stable well region with high stability, and the Ga-enriched n-type region and the Al-enriched n-type region in the n-type cladding layer 21 are formed. The domains are constituted by the first and second quasi-stable n-type domains with high stability, respectively, and the variation in the molar ratio of mixed crystals caused by the drift of the crystal growth device, etc. is also suppressed in the barrier layer 221 . In the barrier layer 221, the Ga-enriched barrier domains 221a that generate the localized presence of carriers are stably formed with AlN molar ratios corresponding to the quasi-stable barrier domains used. As a result, in the barrier layer 221 , the current flows preferentially and stably into the Ga-enriched barrier region, which can further suppress the characteristic variation of the light-emitting element 1 .

The molar ratio of AlN in the platform area TA of the electron barrier layer 23 is approximately in the range of 69% to 90%, compared with the molar ratio of AlN in the well layer 220, it is set to be more than 20%, preferably more than 25% , more preferably 30% or more, set at a high level. Furthermore, the molar ratio of AlN in the Ga-enriched EB region 23a of the electron barrier layer 23 is higher than the molar ratio of AlN in the Ga-enriched well region 220a in the well layer 220, and is set to be more than 20%, preferably 25%. % or more, more preferably 30% or more, is set at a high level.

As a preferred embodiment, in the Ga-enriched well region 220a of the well layer 220, the target value corresponding to the peak emission wavelength and the AlkGa12 _{-kN12 ( k} =3 ~7) is the same as the quasi-stable well region, in the Ga-rich EB region 23a of the electron barrier layer 23, the dominant presence of AlN molar ratio is more than 20% higher than that of AlN in the quasi-stable well region, and the composition of AlGaN The first quasi-stable EB region composed of p-type quasi-stable AlGaN whose ratio is an integer ratio of _{AlmGa12 - mN12} . However, the integer m is 8, 9 or 10. That is, the first quasi-stable EB region existing in the Ga-enriched EB region 23a is three types of Al ₂ Ga ₁ N ₃ , Al ₃ Ga ₁ N ₄ , and Al ₅ Ga ₁ N ₆ , and the AlN molar ratio is each 66.7% (2/3), 75% (3/4), 83.3% (5/6) respectively.

At this time, the composition ratio of AlGaN in the quasi-stable well region (Al _k Ga _12-k N ₁₂ , k=3~7) and the composition ratio of AlGaN in the first quasi-stable EB region (Al _m Ga _12-m N ₁₂ , m= The combination between 8 and 10) is in the combination of m>k+2, which satisfies the above conditions (the difference in AlN molar ratio between the Ga-enriched EB region 23a and the Ga-enriched well region 220a is 20% or more) combination. Therefore, in the above preferred embodiment, within the possible combinations of the integer k and the integer m, (k=6, m=8), (k=7, m=9), and (k=7, m=8) ) is excluded if the above conditions are not met.

The molar ratio of AlN in the platform area TA of the electron barrier layer 23 is in the range of about 69% to 90%, which is more than 1% compared with the molar ratio of AlN in the Ga-enriched EB area 23a, preferably 2% or more, more preferably 4% or more, are set at a high level. In order to fully ensure the localization effect of carriers in the Ga-enriched EB domain 23a, although the difference in AlN molar ratio between the Ga-enriched EB domain 23a in the electron barrier layer 23 and the platform domain TA is set to be 4~5% or more It is better, but at the level of 1~2%, the localization effect of the carrier can be expected.

As a preferred embodiment, the above-mentioned AlGaN composition ratio (AlmGa12 _{-mN12 , m} =8~10) is formed in the Ga-enriched EB region 23a of the electron barrier layer 23, and the AlN molar fraction is In the first quasi-stable EB region of Xe0 (=m/12), the average AlN molar fraction Xea of the electron barrier layer 23 is adjusted to be (m+0.24)/12≦Xea<(m+1) /12 is better. The average AlN molar ratio of the plateau region TA of the electron barrier layer 23 (when the Al-rich EB region is formed, the Al-rich EB region is excluded) is the average AlN molar ratio Xea of the electron barrier layer 23 Slightly the same. Therefore, the difference in molar ratio of AlN between the Ga-enriched EB region 23a serving as the electron barrier layer 23 and the plateau region TA can be ensured to be about 2% or more. More preferably, the upper limit of the adjustment range of the AlN molar fraction Xea is reduced from (m+1)/12 to (m+0.9)/12, which is more stable in the Ga-enriched EB region 23a, and the composition ratio of AlGaN is formed as The first quasi-stable EB field of _{AlmGa12 - mN12} .

However, even if the average AlN molar fraction Xea of the electron barrier layer 23 exceeds the range of (m+0.24)/12≦Xea<(m+1)/12, as long as the slanted area IA of the electron barrier layer 23 The Ga-enriched EB region 23a that forms the localized presence of carriers in the region can obtain a molar ratio of AlN in the Ga-enriched well region 220a corresponding to the well layer 220 in the range of about 69% to 90%. any value.

As a preferred embodiment of the above, the Ga-enriched EB region 23a is constituted by the first quasi-stable EB region with high stability, and the Ga-enriched n-type region and the Al-enriched n-type region in the n-type cladding layer 21 are formed. The n-type domains are respectively composed of the first and second quasi-stable n-type domains with high stability. The effect of the mixed crystal molar ratio variation caused by the drift of the crystal growth device, etc. is also in the electron barrier layer 23. The Ga-rich EB domains 23a where the localized presence of carriers is suppressed in the electron barrier layer 23 are stably formed at the molar ratio of AlN corresponding to the used first quasi-stable EB domains. As a result, in the electron barrier layer 23 , the current flows preferentially and stably into the Ga-enriched EB region 23 a , and further, the characteristic variation of the light-emitting element 1 can be suppressed.

The p-electrode 26 is made of, for example, a multilayer metal film such as Ni/Au, and is formed on the p-type connection layer 24 . The n-electrode 27 is formed of, for example, a multilayer metal film such as Ti/Al/Ti/Au, and is formed on a part of the exposed surface in the second area R2 of the n-type cladding layer 21 . However, the p-electrode 26 and the n-electrode 27 are not limited to the above-described multilayer metal films, and the electrode structures such as the metal constituting each electrode, the number of layers, and the order of layers can be appropriately changed. In FIG. 13, an example of the shape seen from the upper side of the light-emitting element 1 of the p-electrode 26 and the n-electrode 27 is shown. In FIG. 13, the line BL existing between the p-electrode 26 and the n-electrode 27 shows the boundary line between the first region R1 and the second region R2, and is connected to the active layer 22, the electron barrier layer 23, and the p-type The outer peripheral sidewall surfaces of the layer 24 are uniform.

In the present embodiment, as shown in FIG. 13 , the shapes of the first region R1 and the p-electrode 26 in a plane view are taken as an example. Although a comb-shaped shape is used, the shape and arrangement of the first region R1 and the p-electrode 26 in a plane view are used as examples. The system is not limited to the illustration in FIG. 13 .

When a forward bias is applied between the p electrode 26 and the n electrode 27, holes are supplied from the p electrode 26 to the active layer 22, and electrons are supplied from the n electrode 27 to the active layer 22, and the supplied holes and electrons reach the active layer. The layers 22 recombine to emit light. Furthermore, as a result, a forward current flows between the p electrode 26 and the n electrode 27 .

<Manufacturing method of light-emitting element> Next, an example of a method of manufacturing the light-emitting device 1 illustrated in FIG. 6 will be described.

First, the AlN layer 12 contained in the base material portion 10 and the nitride semiconductor layers 21 to 24 contained in the light-emitting element structure portion 20 are sequentially epitaxially deposited on the sapphire substrate 11 through an organic metal compound vapor phase growth (MOVPE) method. Growth and stratification. At this time, the n-type cladding layer 21 is doped with Si as a donor impurity, and the electron barrier layer 23 and the p-type connecting layer 24 are doped with Mg as an acceptor impurity.

In this embodiment, at least the surfaces of the AlN layer 12, the n-type cladding layer 21, the active layer 22 (the well layer 220, the barrier layer 221), and the electron barrier layer 23 are parallel to (0001) The multi-segment platform of the surface, the main surface 11a of the sapphire substrate 11 is inclined at an angle (off angle) within a certain range (for example, 0 degrees to 6 degrees) with respect to the (0001) plane, and the use of the main surface 11a on the main surface 11a shows multi-segment. The slightly inclined substrate of the platform.

As the conditions for the related epitaxial growth, in addition to the use of the (0001) sapphire substrate 11 as the above-mentioned micro-tilted substrate, for example, the growth rate of the terrace that is easy to express a multi-segment shape (specifically, for example, by appropriately setting the growth temperature, Various conditions such as the supply amount or flow rate of the raw material gas or carrier gas to achieve the growth rate) and the like. However, since these conditions are obtained differently depending on the type or structure of the film forming apparatus, it is sufficient to specify these conditions by actually producing several samples in the film forming apparatus.

As a growth condition of the n-type cladding layer 21, after the growth starts, a layered region 21a is formed by the mass movement of Ga in the level difference portion (inclined region) between the multi-stage terraces formed on the upper surface of the AlN layer 12. Then, along with the epitaxial growth of the n-type cladding layer 21, the layered region 21a is accompanied by the mass shift of Ga, and can be grown obliquely upward through segregation, and the growth temperature, growth pressure, and supply body impurity concentration.

Specifically, the growth temperature is preferably 1050°C or higher, where mass shift of Ga is likely to occur, and 1150°C or lower, where n-type AlGaN can be well prepared. In addition, when the growth temperature exceeds the growth temperature of 1170°C, the mass transfer of Ga will be excessive. Even if the first quasi-stable AlGaN, the AlN molar rate is easy to fluctuate randomly, so it is difficult to stably form AlN with a molar rate of 41.7%~ 75% of the n-type quasi-stable AlGaN is the first and second quasi-stable n-type field, so I don't like it. As a growth pressure, 75 Torr or less is preferable as a good growth condition for AlGaN, and as a control limit of a film-forming apparatus, 10 Torr or more is actually preferable. The concentration of impurities in the donor is preferably about 1×10 ¹⁸ to 5×10 ¹⁸ cm ^-3 . However, the above-mentioned growth temperature, growth pressure, etc. are only examples, and the conditions may be suitable and optimal according to the specific film-forming apparatus to be used.

The supply amount and flow rate of the raw material gas (trimethylaluminum (TMA) gas, trimethylgallium (TMG) gas, ammonia gas) or carrier gas used in the organometallic compound vapor phase growth The average AlN molar ratio Xna of 21 was set as a target value.

The average AlN molar fraction Xna of the n-type cladding layer 21 is AlGaN in the first quasi-stable n-type region existing in the Ga _- rich _n -type region, and the AlGaN composition ratio is an integer ratio of AlnGa12- _nN12 ( When n=5~8), set it within the first appropriate range of (n+0.5)/12<Xna<(n+1)/12, more preferably set it within (n+0.5)/12<Xna ≦(n+0.9)/12 within the appropriate range of the second.

In this embodiment, in order to obtain the above-mentioned suitable growth conditions for mass transfer of Ga, the AlN molar ratio Xna within the above-mentioned first or second suitable range is stably formed in the Ga-enriched n-type region. The AlGaN composition ratio becomes the first quasi-stable _n -type region of _AlnGa12 -nN12 in the integer ratio, and in the Al-rich _n -type region, the AlGaN composition ratio becomes the integer ratio of Aln ₊ 1Ga11 _-n . Adjusted for the second quasi-stable n-type region _of N12. However, when the AlN molar fraction Xna is within the above-mentioned second appropriate range, in the Ga-enriched n-type region and the Al-enriched n-type region, the first and second quasi-stable AlGaN composition ratios can more easily be formed stably. n-type field.

In the layered region 21a, the first quasi-stable n-type region where the composition ratio of AlGaN is an integer ratio of AlnGa12 _{-nN12 ( n} =5~8), and the AlN moiety in the first quasi-stable n-type region are stably present. The difference between the audible fraction (n/12) and the average AlN molar fraction (≒Xna) of the n-type body region 21b is as described above, and since the stability is ensured to be about 1/24 (about 4.17%) or more, n The carriers in the type cladding layer 21 are locally localized in the layered region 21a having a smaller bandgap energy than the n-type bulk region 21b.

However, the concentration of the donor impurity depends on the thickness of the n-type cladding layer 21 and does not necessarily need to be uniformly controlled in the vertical direction. For example, the impurity concentration in a specific thin-film thickness portion of the n-type cladding layer 21 is lower than the above-mentioned set concentration, for example, it can be controlled to be less than 1×10 ¹⁸ cm ^-3 , and more preferably less than 1×10 ¹⁷ cm ^-3 the low impurity concentration layer. The thickness of the low impurity concentration layer is preferably greater than 0 nm by 200 nm or less, more preferably 10 nm or more and 100 nm or less, and even more preferably 20 nm or more and 50 nm or less. In addition, the donor impurity concentration of the low-impurity-concentration layer may be lower than the above-mentioned set concentration, and the undoped layer (0 cm ⁻³ ) may be included in a part. Furthermore, it is preferable that a part or all of the low impurity concentration layer is present in the upper layer region within a depth of 100 nm from the upper surface of the n-type cladding layer 21 to the lower side.

In the above-mentioned method, when forming the n-type cladding layer 21 having the layered region 21a and the n-type body region 21b, the entire surface of the upper surface of the n-type cladding layer 21 is formed, and then, through the organic metal compound vapor phase growth (MOVPE) method The active layer 22 (the well layer 220, the barrier layer 221), the electron barrier layer 23, the p-type connection layer 24, and the like are formed by a known epitaxial growth method such as these.

The acceptor impurity concentration of the electron barrier layer 23 is taken as an example, preferably about 1.0×10 ¹⁶ to 1.0×10 ¹⁸ cm ^-3 , and the acceptor impurity concentration of the p-type junction layer 24 is taken as an example, 1.0×10 ¹⁸ to 1.0 The degree of ×10 ²⁰ cm ^-3 is preferred. However, the acceptor impurity concentration does not necessarily need to be uniformly controlled in the vertical direction for the respective film thicknesses of the electron barrier layer 23 and the p-type connection layer 24 .

In the formation of the active layer 22, in the same manner as the n-type cladding layer 21, under the growth conditions that are easy to express the above-mentioned multi-stage terrace, the average AlN mol fraction Xwa of the well layer 220 is set as the target value, The well layer 220 is grown, and the barrier layer 221 is grown with the average AlN molar fraction Xba of the barrier layer 221 as a target value.

The average AlN mole fraction Xwa of the well layer 220 is roughly set in the range of Xw0+2%~Xw0+3% when the Ga-rich well region 220a forms a quasi-stable well region of AlN mole fraction Xw0 .

Furthermore, the average AlN mol fraction Xba of the barrier layer 221 is set at Xb0+2%≦Xba when the quasi-stable barrier region of AlN mol fraction Xb0 is formed in the Ga-enriched barrier region 221a <Xb0+8.33%.

In the formation of the electron barrier layer 23, in the same manner as the n-type cladding layer 21, under the growth conditions that are easy to express the above-mentioned multi-segment platform, the average AlN molar ratio of the electron barrier layer 23 is divided. The electron barrier layer 23 is grown with the rate Xea as a target value.

The average AlN mole fraction Xea of the electron barrier layer 23 is in the Ga-enriched EB region 23a of the electron barrier layer 23, and is set at Xe0 when the first quasi-stable EB region of the AlN mole fraction Xe0 is formed. +2%≦Xea＜Xe0+8.33%.

In this embodiment, the long temperature of the active layer 22 (the well layer 220, the barrier layer 221), the electron barrier layer 23, and the p-type connection layer is set to be T1 for the growth temperature of the n-type cladding layer 21, so that the active layer When the growth temperature of the layer 22 is T2, the growth temperature of the electronic barrier layer 23 is T3, and the growth temperature of the p-type connection layer is T4, within these preferred temperature ranges (1050°C~1170°C), it satisfies The relationship represented by the following formulae (1) and (2) is preferable. T3≧T2 (1) T3>T1>T4 (2)

Furthermore, the relationship of the above formula (1) is the following formula when the AlN molar ratio of the first quasi-stable EB region in the first Ga-enriched region 23a of the electron barrier layer 23 is 83.3% or 75% (1A) is preferable, and when the molar fraction of AlN in the first quasi-stable EB region is 66.7%, the following formula (1B) is preferable. This is because when the molar ratio of AlN in the first quasi-stable EB region increases, a higher growth temperature is required to promote the mass transfer of Ga. T3≧T2+50℃ (1A) T2+50℃＞T3≧T2 (1B)

Furthermore, when the growth temperature T3 of the electron barrier layer 23 is 83.3% of the AlN molar fraction in the first quasi-stable EB area, preferably above 1150°C, the AlN molar fraction in the first quasi-stable EB area is 75 % or 66.7%, it is better to be above 1100°C, and even better than the high temperature of 1100°C. However, each of the above-mentioned temperatures is just an example, such as increasing the flow rate of the nitrogen source gas. By reducing the growth rate, the above-mentioned 1150°C and 1100°C can be reduced to 1100°C and 1050°C, respectively.

However, when the growth temperature T3 of the electron barrier layer 23 is increased from the growth temperature T2 of the active layer 22, the decomposition of GaN occurs in the well layer 220 at the lower position during the migration of the growth temperature. The decomposition of GaN may deteriorate the characteristics of the light-emitting element 1 . Therefore, in order to suppress the decomposition of GaN, between the uppermost well layer 220 and the electron barrier layer 23, in order to prevent the decomposition of GaN, a film thinner than the barrier layer 221 (for example, 3 nm or less, preferably 2 nm or less), it is preferable to form an AlGaN layer or an AlN layer with a higher molar fraction of AlN than the barrier layer 221 and the electron barrier layer 23 .

As an example of growth conditions other than the growth temperature for promoting the mass transfer of Ga in the electron barrier layer 23, when the growth temperature T3 is 1150°C, the flow rate ratio (V/III) of the source gas is set to 5000 to 6000, and the growth The speed is preferably about 150 nm/h.

The above formulas (1A) and (2) will satisfy the growth temperatures T1 to T4 of the n-type cladding layer 21, the active layer 22 (well layer 220, the barrier layer 221), the electron barrier layer 23, and the p-type connection layer. ) is shown below. T1=T2=1080℃, T3=1150℃, T4=980℃

One example of the above-mentioned growth temperatures T1 to T4 is that the AlN molar fraction Xn0 in the first quasi-stable n-type region in the layered region 21a of the n-type cladding layer 21 and the Ga-enriched well in the well layer 220 are shown below. The AlN molar ratio Xw0 in the quasi-stable well zone in the zone 220a, the AlN molar ratio Xb0 in the quasi-stable barrier zone in the barrier layer 221, the Ga-enriched barrier zone in the barrier layer 221a, and the electron barrier layer 23 The AlN molar ratio Xe0 of the first quasi-stable EB field in the Ga-enriched EB field 23a is applied. Xn0=41.7%, 50%, 58.3%, 66.7% Xw0=0%, 25%, 33.3%, 41.7%, 50%, 58.3% Xb0=50%, 58.3%, 66.7%, 75%, 83.3% Xe0=66.7%, 75%, 83.3%

In the above method, when the active layer 22 (the well layer 220, the barrier layer 221), the electron barrier layer 23, the p-type connection layer 24, etc. are formed on the entire surface of the upper surface of the n-type cladding layer 21, then, through the A well-known etching method such as reactive ion etching is used to selectively etch the second region R2 of the nitride semiconductor layers 21 to 24 to expose the upper surface of the n-type cladding layer 21, and to expose the second region R2 on the upper surface of the n-type cladding layer 21. 2 Domain R2 Section. Then, the p-electrode 26 is formed on the p-type connection layer 24 in the unetched first region R1 by a known film-forming method such as electron beam evaporation, and the n in the first region R2 is etched at the same time. On the type cladding layer 21, an n-electrode 27 is formed. However, after the formation of one or both of the p-electrode 26 and the n-electrode 27 , heat treatment may be performed by a known heat treatment method such as RTA (instantaneous thermal annealing).

However, the light-emitting element 1 is taken as an example. After flip-chip mounting on a submount, etc., the light-emitting element 1 is sealed with a specific resin (such as a lens-shaped resin) such as polysiloxane or amorphous fluororesin. be used in the state.

The cross-sectional structure of the AlGaN-based semiconductor layers 21 to 24 of the light-emitting element 1 produced in the above manner is a sample before the etching of the p-2 region R2 and the formation of the electrode 26 and the n-electrode 27, and will have vertical (or slightly vertical) The test piece of the cross-section on the upper surface of the data was processed by a focused ion beam (FIB), and observed through the HAADF-STEM image of the test piece.

Furthermore, the composition analysis in a specific semiconductor layer among the AlGaN-based semiconductor layers 21 to 24 can be performed by energy dispersive X-ray spectroscopy (cross-sectional TEM-EDX) or CL (cathode ray luminescence) method using the above-mentioned sample pieces. conduct. Although the description of the composition analysis by the cross-section TEM-EDX is omitted, in the descriptions of the prior applications (PCT/JP2020/023050, PCT/JP2020/024828, PCT/JP2020/026558, PCT/JP2020/031620) of the present inventor, There are detailed instructions.

<Results of composition analysis of n-type cladding layer> Next, the results of measuring the AlN molar fraction in the layered region 21a and the n-type bulk region 21b in the n-type cladding layer 21 by the CL (cathode ray luminescence) method will be described.

For the composition analysis of the n-type cladding layer 21, two types of samples were prepared, and the sample pieces having the cross section perpendicular (or slightly perpendicular) to the upper surface of the n-type cladding layer 21 from each sample were subjected to a focused ion beam (FIB). After processing, two test pieces A and B for measurement were produced.

The sample of the sample piece A is formed by sequentially depositing the n-type cladding layer 21, and the relatively low-level cladding layer 21 on the base material portion 10 formed from the above-mentioned sapphire substrate 11 and the AlN layer 12 according to the above-mentioned manufacturing method of the n-type cladding layer 21 and the like. The n-type cladding layer 21 is formed by an AlGaN layer with a high AlN molar ratio, an AlGaN layer for protecting the surface of the sample, and a resin film for protecting. However, in the preparation of this sample, the sapphire substrate 11 whose main surface has an off-angle with respect to the (0001) plane was used, and the base material portion 10 showing a multi-stage terrace was used on the surface of the AlN layer 12 . However, in the preparation of this sample, the film thickness of the n-type cladding layer 21 was 3.1 μm, and the average AlN molar ratio Xna (target value) of the n-type cladding layer 21 was 63%. The value determined by RBS analysis of AlN molar fraction Xna was also 63%. Furthermore, the donor impurity concentration was set to about 3×10 ¹⁸ cm ⁻³ , and the implantation amount of the donor impurity (Si) was controlled.

The sample of the sample piece B is formed by sequentially depositing the n-type cladding layer 21 and the active layer on the base material portion 10 formed from the above-mentioned sapphire substrate 11 and the AlN layer 12 according to the above-mentioned manufacturing method of the n-type cladding layer 21 and the like. The layer 22 and the n-type cladding layer 21 are formed of an AlGaN layer having a higher molar fraction of AlN, an AlGaN layer for protecting the surface of the sample, and a protective resin film. However, in the preparation of this sample, the sapphire substrate 11 whose main surface has an off-angle with respect to the (0001) plane was used, and the base material portion 10 showing a multi-stage terrace was used on the surface of the AlN layer 12 . However, in the preparation of this sample, the film thickness of the n-type cladding layer 21 is about 2.6 μm, and the film thickness of the lower side is about 1 μm, and the average AlN molar ratio of the n-type cladding layer 21 is Xna The (target value) is 55%, and the average AlN molar ratio Xna (target value) of the n-type cladding layer 21 is 43% with respect to the upper film thickness of about 1.6 μm. The value determined by the RBS analysis method of AlN molar fraction Xna is also 55% on the lower side and 43% on the upper side. Furthermore, on both the upper side and the lower side, the donor impurity concentration was about 3×10 ¹⁸ cm ⁻³ , and the implantation amount of the donor impurity (Si) was controlled.

FIG. 14 shows a scanning electron microscope (SEM) image of the main part of the n-type cladding layer 21 on the measurement section including the above-mentioned sample piece A. As shown in FIG. FIG. 15 is an SEM image showing the main part of the n-type cladding layer 21 on the measurement section including the above-mentioned sample piece B. As shown in FIG.

The measurement range of the sample A (the range of the incident point of the electron beam irradiated for the measurement) is in the X direction (the horizontal direction parallel to the second plane) and the Y direction (the vertical direction perpendicular to the second plane), They are 6.25 μm and 3.2 μm, respectively, and the incident points of the electron beams are set in a grid pattern of 121 meshes×60 meshes. The mesh spacer is about 52 nm in the X direction and about 53 nm in the Y direction. The measurement range of the sample piece B was 6.25 μm and 4.6 μm in the X direction and the Y direction, respectively, and the incident points of the electron beams were set in a grid pattern of 125 meshes and 93 meshes. The mesh spacing is 50 nm in both the X direction and the Y direction. However, the main part on the measurement cross section of the sample piece A shown in FIG. 14 shows a square area (3.2 μm×3.2 μm) of a part of the above-mentioned measurement range (6.25 μm×3.2 μm). In addition, the main part on the measurement cross section of the sample piece B shown in FIG. 15 shows the square area (3.25 μm×3.25 μm) of a part of the above-mentioned measurement range (6.25 μm×4.6 μm).

The Y value (Y coordinate) in each measurement range of the sample pieces A and B shown in FIGS. 14 and 15 represents the number of meshes counted from the upper end of each measurement range, and Y=0 at the upper end of each graph. In FIG. 14, Y=3 and Y=58 correspond to the upper end and the lower end of the n-type cladding layer 21, respectively. In FIG. 15, Y=7 and Y=58 correspond to the upper end and the lower end of the n-type cladding layer 21, respectively.

The electron beam with a beam diameter of 50 nm (diameter) was irradiated once at the incident point of the grid-shaped electron beam in each measurement range of the sample piece A and the sample piece B, and the CL spectrum of each incident point was measured.

Fig. 16 shows that among the five Y coordinates of Y=7, Y=15, Y=30, Y=43, and Y=56 of each sample A, for the 121 CL spectra obtained by scanning in the X direction, the following requirements are used. The 1st CL spectrum (solid line) and the 2nd CL spectrum (dashed line) are shown. The first and second CL spectra of the five Y-coordinates are shifted from their respective origins in the vertical axis direction, and are shown on the same graph so as to be recognizable from each other. The vertical axis of FIG. 16 shows the luminous intensity (arbitrary unit), and the luminous intensity of a part of the Y-coordinates (Y=30, 43, 56) is doubled for easy identification. The horizontal axis of FIG. 16 shows wavelength (nm).

The first CL spectrum of each Y-coordinate shown in FIG. 16 is a CL spectrum of the same Y-coordinate, and the peak of the luminous intensity is shifted to the vicinity of the same wavelength on the longer wavelength side than the average AlN molar ratio Xna (63%). CL spectrum, extract more than 6~7 points, and calculate the extracted CL spectrum on average. In addition, the second CL spectrum of each Y coordinate shown in FIG. 16 is from the CL spectrum of the same Y coordinate, and the peak of the luminous intensity is shifted to the vicinity of the same wavelength on the shorter wavelength side than the average AlN molar ratio Xna (63%). For the shifted CL spectrum, extract more than 6 to 7 points, and average the extracted CL spectrum.

Fig. 17 shows that among the four Y coordinates of Y=42, Y=45, Y=50, and Y=55 of the lower portion of each sample piece B, for 125 CL spectra obtained by scanning in the X direction, the following equations are used. The 3rd CL spectrum (solid line) and the 4th CL spectrum (dashed line) are shown. The 3rd and 4th CL spectra of the four Y-coordinates are shifted from their respective origins in the vertical axis direction, and are shown on the same graph so as to be recognizable from each other. The vertical axis of FIG. 17 shows the luminous intensity (arbitrary unit). The horizontal axis of FIG. 17 shows wavelength (nm).

The 3rd CL spectrum of each Y coordinate shown in Fig. 17 is a CL spectrum of the same Y coordinate, and the peak of the luminous intensity is shifted to the vicinity of the same wavelength on the longer wavelength side than the average AlN molar ratio Xna (55%). CL spectrum, extract more than 6~7 points, and calculate the extracted CL spectrum on average. In addition, the 4th CL spectrum of each Y coordinate shown in FIG. 17 is from the CL spectrum of the same Y coordinate, and the peak of the luminous intensity is shifted to the vicinity of the same wavelength on the shorter wavelength side than the average AlN molar ratio Xna (55%). For the shifted CL spectrum, extract more than 6 to 7 points, and average the extracted CL spectrum.

18 shows that among the five Y coordinates of Y=10, Y=15, Y=20, Y=27, and Y=35 of the upper portion of each sample piece B, for 125 CL spectra obtained by scanning in the X direction, The 5th CL spectrum (solid line) and the 6th CL spectrum (dashed line) are shown below. The fifth and sixth CL spectra of the five Y-coordinates are shifted from their respective origins in the vertical axis direction, and are shown on the same graph so as to be recognizable from each other. The vertical axis of FIG. 18 shows the luminous intensity (arbitrary unit). The horizontal axis of FIG. 18 shows wavelength (nm).

The 5th CL spectrum of each Y coordinate shown in FIG. 18 is a CL spectrum of the same Y coordinate, and the peak of the luminous intensity is shifted to the vicinity of the same wavelength on the longer wavelength side than the average AlN molar ratio Xna (43%). CL spectrum, extract more than 6~7 points, and calculate the extracted CL spectrum on average. In addition, the sixth CL spectrum of each Y coordinate shown in FIG. 18 is from the CL spectrum of the same Y coordinate, and the peak of the luminous intensity is shifted to the vicinity of the same wavelength on the shorter wavelength side than the average AlN molar ratio Xna (43%). For the shifted CL spectrum, extract more than 6 to 7 points, and average the extracted CL spectrum.

The beam diameter of the electron beam is 50 nm (diameter), and the width of the cross-section perpendicular to the extending direction of the layered region 21a is about 20 nm on average. In the irradiation range of the electron beam at one incident point, there is a layered region. When the Ga-enriched n-type region of 21a is formed, an Al-enriched n-type region exists at the edge portion of the n-type body region 21b adjacent to the layered region 21a.

Therefore, the 1st, 3rd, and 5th CL spectra shifted to the longer wavelength side of the more average AlN molar fraction Xna are in the irradiation range of the electron beam, and there is a CL spectrum in the Ga-enriched n-type region, which emits light. The intensity peaks are located near wavelengths corresponding to the molar ratio of AlN in the Ga-rich n-type domain. Furthermore, in this irradiation range with a beam diameter of 50 nm, since there is an Al-rich n-type region, there is a second peak of luminous intensity near the wavelength of the AlN molar ratio in the Al-rich n-type region. situation.

In addition, the second, fourth, and sixth CL spectra shifted to the shorter wavelength side of the more average AlN molar fraction Xna are within the irradiation range of the electron beam, and there is no Ga-enriched n-type region, but Al-enriched. In the CL spectrum of the n-type domain, the peak of the luminescence intensity is located near the wavelength corresponding to the molar ratio of AlN in the Al-enriched n-type domain.

The average AlN molar ratio Xna (=63%) of the n-type cladding layer 21 of the sample piece A is adjusted to be (n+0.5)/12<Xna<(n+1) when the integer n is 7 /12 within the first appropriate range, and (n+0.5)/12 <Xna≦(n+0.9)/12 within the second appropriate range. Then, in the Ga _- enriched n-type region _of the layered region 21a, there is a first quasi-stable n-type region (AlN molar ratio of 58.3%, which is converted into wavelength by AlGaN composition ratio of _Al7Ga5N12 ) About 266nm), in the Al-enriched n-type region of the n-type body region 21b, there is a second quasi-stable n-type region with AlGaN composition ratio of Al ₂ Ga ₁ N ₃ (AlN molar ratio is 66.7%, converted into wavelength is about 253 nm).

The peaks of the luminescence intensity of the first CL spectrum of the five Y-coordinates (Y=7, 15, 30, 43, 56) shown in Fig. 16 are in the range of about 264 nm to about 267 nm, all located near 266 nm, which can be seen from In each Y coordinate, in the Ga _- enriched n-type region _of the layered region 21a, there is a first quasi-stable n-type region of _Al7Ga5N12 whose AlGaN composition ratio is an integer ratio. And more. The peaks of the luminescence intensity of the 2 CL spectrum of the above-mentioned five Y-coordinates shown in FIG. 16 are in the range of about 252 nm to about 255 nm, and all are located in the vicinity of about 253 nm. In the Al-enriched n-type region, there is a second quasi-stable n-type region of Al ₂ Ga ₁ N ₃ in which the composition ratio of AlGaN is an integer ratio.

The average AlN molar fraction Xna (=55%) of the lower portion of the n-type cladding layer 21 of the sample piece B with a film thickness of about 1 μm is adjusted to be (n+0.5)/ 12<Xna<(n+1)/12 is within the first appropriate range, and (n+0.5)/12<Xna≦(n+0.9)/12 is within the second appropriate range. Therefore, in the Ga-enriched n-type region of the layered region 21a, there is a first quasi-stable n-type region with a composition ratio of AlGaN of Al ₁ Ga ₁ N ₂ (AlN molar ratio is 50%, when converted into wavelength: About 279nm), in the Al-enriched n-type region of the n-type body region 21b, there is a second quasi-stable n-type region with AlGaN composition ratio of Al ₇ Ga ₅ N ₁₂ (AlN molar ratio is 58.3%, converted into wavelength is about 266 nm).

The peaks of the luminescence intensity of the 3rd CL spectrum of the 4 Y coordinates (Y=42, 45, 50, 55) shown in Fig. 17 are in the range of about 276 nm to about 279 nm, and they are all located near about 279 nm. It can be seen that each Y In the coordinates, in the Ga-rich n-type region of the layered region 21a, there is a first quasi-stable n-type region of Al ₁ Ga ₁ N ₂ whose AlGaN composition ratio is an integer ratio. And more. The peaks of the luminescence intensity of the 4 CL spectrum of the above-mentioned four Y-coordinates shown in FIG. 17 are in the range of about 265 nm to about 267 nm, and all are located around 266 nm. It can be seen that in each Y-coordinate, in the n-type body region 21b In the Al-rich n-type region, there is a second quasi-stable n-type region of Al ₇ Ga ₅ N ₁₂ in which the composition ratio of AlGaN is an integer ratio.

The average AlN molar fraction Xna (=43%) of the upper portion of the n-type cladding layer 21 of the sample piece B with a film thickness of about 1.6 μm is not adjusted to be (n+0.5) when the integer n is 5 /12<Xna<(n+1)/12 is within the first appropriate range, and (n+0.5)/12<Xna≦(n+0.9)/12 is within the second appropriate range, adjusted to n/ 12<Xna<(n+0.5)/12. Therefore, in the Ga _- enriched n-type region _of the layered region 21a, although there is a first quasi-stable n-type region (AlN molar ratio of 41.7%, which is converted into a wavelength of AlGaN with a composition ratio of _Al5Ga7N12 ) is about 293 nm), in the Al-enriched n-type region of the n-type body region 21b, there is a second quasi-stable n-type region with AlGaN composition ratio of Al ₁ Ga ₁ N ₂ (AlN molar ratio is 50%, converted The probability of forming a wavelength of about 279 nm) is low.

The peaks of the luminescence intensity of the 5th CL spectrum of the five Y-coordinates (Y=10, 15, 20, 27, 35) shown in Fig. 18 are in the range of about 291 nm to about 293 nm, and they are all located near 293 nm, which can be seen from In each Y coordinate, in the Ga _- enriched n-type region _of the layered region 21a, there is a first quasi-stable n-type region of _Al5Ga7N12 whose AlGaN composition ratio is an integer ratio. And more. The peaks of the luminescence intensity of the 2 CL spectrum of the above-mentioned five Y-coordinates shown in FIG. 18 are in the range of about 283 nm to about 285 nm, and in all the five Y-coordinates, they are located on the higher wavelength side than about 279 nm. In the coordinates, in the Al-rich n-type region of the n-type body region 21b, the second quasi-stable n-type region where the AlGaN composition ratio is an integer ratio of Al ₁ Ga ₁ N ₂ does not dominate. This is quite schematically the situation shown in the right part of FIG. 7 .

As described above, both the sample piece A (integer n=7, Xna=63%) and the lower part of the sample piece B (integer n=6, Xna=55%) are adjusted to the average AlN molar ratio Xna It is within the first suitable range of (n+0.5)/12<Xna<(n+1)/12, and the second suitable range of (n+0.5)/12<Xna≦(n+0.9)/12 Within the range, in the Ga _- enriched _n -type region _of the layered region 21a and the Al-enriched n-type region of the n-type bulk region 21b, there are AlnGa12-nN12 and Aln ₊ whose composition ratio of AlGaN is an integer ratio. The first and second quasi-stable n-type domains of ₁ Ga _11-n N ₁₂ are provided with the element structure of the light-emitting element 1 of the first embodiment.

On the other hand, the upper portion of the sample piece B (integer n=5, Xna=43%) was not adjusted to the average AlN molar ratio Xna so that (n+0.5)/12<Xna<(n+1)/ Within the first appropriate range of 12, and within the second appropriate range of (n+0.5)/12<Xna≦(n+0.9)/12, the result is that the Al in the n-type body region 21b is rich in n The second quasi-stable n-type region where AlGaN composition ratio is an integer ratio of Aln ₊ 1Ga11 _{- nN12} does not dominate the second quasi-stable n-type region, which is different from the element structure of the light-emitting element 1 of the first embodiment.

[Second Embodiment] In the light-emitting element 1 of the first embodiment, as a preferred embodiment, in the Ga-enriched EB region 23a of the electron barrier layer 23, the dominant presence of AlN molar quasi-stable wells will be described. The AlN molar ratio of the field is higher than 20%, and the AlGaN composition ratio is an integer ratio of AlmGa12 _{-mN12 ( m} =8~10) p-type quasi-stable AlGaN formed the first quasi-stable EB field, The average AlN molar fraction Xea of the electron barrier layer 23 is adjusted to be within the range of (m+0.24)/12≦Xea<(m+1)/12. Furthermore, as a preferred embodiment, in the electron barrier layer 23, at the edge portion of the terrace area TA adjacent to the inclined area IA, the average AlN molar ratio Xea of the electron barrier layer 23 is used as a reference. , the formation of Al-enriched EB domains with high AlN molar fraction.

In the light-emitting element 1 of the second embodiment, as a preferred embodiment, in the Ga-enriched EB region 23a of the electron barrier layer 23, the AlN molar region where the AlN molar ratio is relatively stable well is dominated The rate is higher than 20%, and the AlGaN composition ratio is an integer ratio of _{AlmGa12 - mN12} . The p-type quasi-stable AlGaN forms the first quasi-stable EB field. At the same time, the Al-enriched EB in the electron barrier layer 23 In the field, the second quasi-stable EB field is dominated by the presence of p-type quasi-stable AlGaN whose AlGaN composition ratio is an integer ratio of Alm ₊ 1Ga11 _{- mN12} . At this time, the adjustment range of the average AlN molar ratio Xea of the electron barrier layer 23 is narrower than the range described in the first embodiment, and the AlN molar ratio Xea is adjusted to be (m+0.5)/ In the first appropriate range of 12<Xea<(m+1)/12, it is more preferable to adjust to be in the second appropriate range of (m+0.5)/12<Xea≦(m+0.9)/12. However, the integer m is 8 or 9.

Therefore, in the second embodiment, in the method for manufacturing the light-emitting device 1, in the manner described in the first embodiment, the active layer 22 is formed on the sapphire substrate 11 by the MOVPE method, and then the electron barrier layer 23 is formed. , and film formation was performed by setting the supply amount and flow rate of the source gas or carrier gas, and the AlN molar fraction Xea as target values. The growth temperature of the electron barrier layer 23 is basically as described in the first embodiment, and the AlN molar fraction Xea is set to be higher than that in the first embodiment. can be adjusted within the range.

When the integer m is 10, in the Ga-enriched EB region 23a, although the quasi-stable AlGaN whose composition ratio is Al ₅ Ga ₁ N ₆ of the p-type exists stably as the first quasi-stable EB region, in the Al-rich EB region It is difficult to stably dominate the existence _of p-type quasi-stable AlGaN with _a composition ratio of _Al11Ga1N12 . The reason for this is that when the composition ratio of AlGaN is Al ₁₁ Ga ₁ N ₁₂ , the molar ratio of AlN is extremely high as high as 91.7% (11/12), and the Ga that is easy to move enters the position of symmetrical arrangement, and the amount of Al is large. When entering the position randomly, there is a high possibility that the atomic arrangement of Al and Ga cannot be symmetrical, and the atomic arrangement of Al and Ga is close to a random state, which is because the stability of quasi-stable AlGaN will decrease.

Since the integer m is 8 or 9, the composition ratio of AlGaN in the quasi-stable well region (Al _k Ga _12-k N ₁₂ (k=3~7)) and the first quasi-stable EB region (Al _m Ga _12-m N ₁₂ When the combination of the AlGaN composition ratios of ) corresponds to the condition of m>k+2 described in the first embodiment, the combination with k=7 is not an appropriate combination.

In the second embodiment, Al ₇ Ga ₅ N ₁₂ (AlN molar ratio = 58.3%) is excluded from the AlGaN composition ratio in the quasi-stable well region, and the AlGaN composition ratio in the quasi-stable well region (Al _k Ga _{12- k} N ₁₂ (k=3~6)) and the AlGaN composition ratio of the first quasi-stable n-type region in the layered region 21a in the n-type cladding layer 21 is an integer ratio of Al _n Ga _12-n N ₁₂ ( The relationship (n≧k+1) described in the first embodiment between n=5 to 8) is maintained as it is.

In the second embodiment, by forming the Ga-rich EB domain 23a and the Al-rich EB domain as the first and second quasi-stable EB domains with high stability, respectively, drift or the like caused by the crystal growth apparatus can be further suppressed. The variation of the mixed crystal molar ratio, in the electron barrier layer 23, produces the localized Ga-rich EB domain 23a of the carrier, which corresponds to the AlN molar ratio of the first quasi-stable EB domain used stably be formed. As a result, in the electron barrier layer 23 , the current flows preferentially and stably into the Ga-enriched EB region 23 a , and further, the characteristic variation of the light-emitting element 1 can be suppressed.

The base material portion 10 of the light-emitting element 1 of the second embodiment, and the AlGaN-based semiconductor layers 21 to 24 , the p-electrode 26 , and the n-electrode 27 of the light-emitting element structure portion 20 are in the electron barrier layer 23 except for the Al-rich EB region The portion where the second quasi-stable EB region exists internally, and the AlN molar ratio Xea adjusted so that the uniformity of the electron barrier layer 23 becomes (m+0.5)/12<Xea<(m+1)/12 Within the appropriate range of 1, it is more preferable to be (m+0.5)/12<Xea≦(m+0.9)/12, which is outside the part within the appropriate range of 2, and the basis of the light-emitting element 1 of the first embodiment. Since the AlGaN-based semiconductor layers 21 to 24 , the p-electrode 26 , and the n-electrode 27 of the material portion 10 and the light-emitting element structure portion 20 are the same, overlapping descriptions are omitted.

[Third Embodiment] In the light-emitting element 1 of the third embodiment, as in the light-emitting element 1 of the second embodiment, it is explained that the presence of AlN in the Ga-enriched EB region 23a of the electron barrier layer 23 dominates the molar ratio Compared with the AlN molar ratio in the quasi-stable well field, the molar ratio is more than 20%, and the AlGaN composition ratio is the integer ratio of _{AlmGa12 - mN12} p-type quasi-stable AlGaN to form the first quasi-stable EB field. In the Al-enriched EB region of the electron barrier layer 23, the second quasi-stable EB region formed by the presence of p-type quasi-stable AlGaN of Alm ₊ 1Ga11 _{- mN12} whose composition ratio is an integer ratio dominates. Furthermore, the adjustment range of the average AlN molar ratio Xea of the electron barrier layer 23 is narrower than that described in the first embodiment, and the AlN molar ratio Xea is adjusted to be (m+0.5)/ In the first appropriate range of 12<Xea<(m+1)/12, it is more preferable to adjust to be in the second appropriate range of (m+0.5)/12<Xea≦(m+0.9)/12. However, the integer m is 8 or 9.

Therefore, in the third embodiment, in the method of manufacturing the light-emitting device 1, the active layer 22 is formed on the sapphire substrate 11 by the MOVPE method in the manner described in the first embodiment, and then the electron barrier layer 23 is formed. , and film formation was performed by setting the supply amount and flow rate of the source gas or carrier gas, and the AlN molar fraction Xea as target values. The growth temperature of the electron barrier layer 23 is basically as described in the first embodiment, and the AlN molar fraction Xea is set to be higher than that in the first embodiment. can be adjusted within the range.

Furthermore, as described in the second embodiment, the composition ratio of AlGaN in the quasi-stable well region (Al _k Ga _12-k N ₁₂ (k=3~7)) and the first quasi-stable EB region (Al _m Ga _12-m Since the combination between the AlGaN composition ratios of N ₁₂ ) is an integer m of 8 or 9, the combination with k=7 cannot be an appropriate combination. Furthermore, although Al ₇ Ga ₅ N ₁₂ (AlN molar ratio=58.3%) was excluded from the AlGaN composition ratio in the quasi-stable well region, the AlGaN composition ratio in the quasi-stable well region (Al _k Ga _12-k N ₁₂ (k=3~6)) and the AlGaN composition ratio of the first quasi-stable n-type region in the layered region 21a in the n-type cladding layer 21 is an integer ratio of AlnGa12 _{-nN12 ( n} =5 The relationship (n≧k+1) described in the first embodiment between ~8) is maintained as it is.

In the light-emitting element 1 of the third embodiment, similarly to the light-emitting elements 1 of the first and second embodiments, the n-type cladding layer 21 is formed of an n-type AlGaN-based semiconductor, and inside the n-type cladding layer 21, In the n-type cladding layer 21 , there are uniformly dispersed layered regions 21 a with low AlN molar fraction locally. Therefore, in the layered region 21a, as described above in the section of the prior art, since the bandgap energy is locally reduced, the carriers are easily localized and operate as a low-impedance current path.

However, in the light-emitting element 1 of the third embodiment, unlike the light-emitting element 1 of the first and second embodiments, there is no need for the presence of Al in the Ga-enriched n-type region of the layered region 21a where the composition ratio of AlGaN is an integer ratio. In the first quasi-stable n-type region of _n Ga _12-n N ₁₂ (n=5~8), in the Al-rich n-type region of the n-type body region 21b, there is Al _n+1 whose AlGaN composition ratio is an integer ratio The second quasi-stable n-type region of Ga _11-n N ₁₂ and the n-type body region 21b form an Al-enriched n-type region. However, as a preferred embodiment, in the Ga-rich n-type region of the layered region 21a, there may be a first AlGaN composition ratio of AlnGa12 _{-nN12 ( n} =5~8) in which the composition ratio is an integer ratio. A quasi-stable n-type domain, and/or an Al-enriched n-type domain may be formed in the n-type body domain 21b.

In the Ga-enriched n-type region of the layered region 21a, when there is a first quasi-stable n-type region of AlnGa12 _{- nN12} ( _n =5~8) whose composition ratio of AlGaN is an integer ratio, the n-type The average AlN molar fraction Xna of the coating layer 21 is preferably in the range of (n+0.24)/12<Xna<(n+1)/12.

That is, in the light-emitting element 1 of the third embodiment, similarly to the light-emitting elements 1 of the first and second embodiments, the localization of carriers is likely to occur in the layered regions 21a and 21a of the n-type cladding layer 21, respectively. The well layer 220 is a Ga-enriched well region 220a, the barrier layer 221 is a Ga-enriched barrier region 221a, and the electron barrier layer 23 is a Ga-enriched EB region 23a.

On the other hand, with regard to the variation in characteristics of the light-emitting element 1 due to drift of the crystal growth device, etc., in the light-emitting element 1 of the first embodiment, the Ga-enriched n-type region in the n-type cladding layer 21 and the The Al-enriched n-type domains are respectively constituted by the first and second quasi-stable n-type domains with high stability, mainly in the n-type cladding layer 21, to enhance the suppression of the variation in mixed crystal molar ratio, the third In the light-emitting element 1 of the embodiment, the Ga-rich EB region 23a and the Al-rich EB region in the electron barrier layer 23 are constituted by the first and second quasi-stable EB regions with high stability, respectively. In the electron barrier layer 23, the suppression of the variation of the molar ratio of the mixed crystal is enhanced. However, in the light-emitting element 1 of the second embodiment, both in the n-type cladding layer 21 and in the electron barrier layer 23 are enhanced to suppress the fluctuation of the mixed crystal molar ratio.

The base material portion 10 of the light-emitting element 1 of the third embodiment, the AlGaN-based semiconductor layers 21 to 24 , the p-electrode 26 , and the n-electrode 27 of the light-emitting element structure portion 20 are adjusted to be n-type in the n-type cladding layer 21 . In the Al-enriched n-type region of the bulk region 21b, the portion _of the second quasi-stable n-type region where the composition ratio of AlGaN becomes an integer ratio of Aln ₊ 1Ga11 _- nN12 dominates, and in the electron barrier layer 23 In the Al-enriched EB domain, the AlN molar ratio Xea that dominates the portion where the second quasi-stable EB domain exists, and the average of the electron barrier layer 23 is (m+0.5)/12<Xea<(m+1) The first suitable range of /12 is more preferably (m+0.5)/12<Xea≦(m+0.9)/12 the part outside the suitable range of the second, and the light emission of the first embodiment Since the base material portion 10 of the element 1 and the AlGaN-based semiconductor layers 21 to 24 , the p-electrode 26 , and the n-electrode 27 of the light-emitting element structure portion 20 are the same, overlapping descriptions are omitted.

[4th Embodiment] In the light-emitting element 1 of the first to third embodiments, the p-type layer constituting the light-emitting element structure portion 20 is two layers of the electron barrier layer 23 and the p-type connecting layer 24, but in the light-emitting element 2 of the fourth embodiment, The p-type layer is between the electron barrier layer 23 and the p-type connection layer 24 and has a p-type cladding layer 25 composed of one or more p-type AlGaN-based semiconductors.

Therefore, in the fourth embodiment, as shown in FIG. 19 , the AlGaN-based semiconductor layers 21 to 25 of the light-emitting element structure portion 20 are provided with an n-type cladding layer 21 (n-type layer) sequentially from the base portion 10 side. , the active layer 22, the electron barrier layer 23 (p-type layer), the p-type cladding layer 25 (p-type layer) and the p-type connection layer 24 (p-type layer) are sequentially epitaxially grown and stacked.

The base material portion 10 of the light-emitting element 2 of the fourth embodiment, and the AlGaN-based semiconductor layers 21 to 24, the p-electrode 26, and the n-electrode 27 of the light-emitting element structure portion 20 emit light according to any one of the first to third embodiments. Since the base material portion 10 of the element 1 and the AlGaN-based semiconductor layers 21 to 24 , the p-electrode 26 , and the n-electrode 27 of the light-emitting element structure portion 20 are the same, overlapping descriptions are omitted.

The p-type cladding layer 25 is the AlN layer 12 of the base material portion 10 , which is sequentially epitaxially grown with the main surface 11 a of the sapphire substrate 11 , and the n-type cladding layer 21 of the light-emitting element structure portion 20 and each semiconductor in the active layer 22 The layer is the same as the electron barrier layer 23, and has a surface derived from the main surface 11a of the sapphire substrate 11 to form a multi-segment platform parallel to the (0001) plane.

In FIG. 20, an example of the laminated structure (multiple quantum well structure) of the well layer 220 of the active layer 22 and the barrier layer 221 is shown schematically. In FIG. 20 , in the first embodiment, a p-type cladding layer 25 is formed on the electron barrier layer 23 having the laminated structure described with reference to FIG. 8 .

In the p-type cladding layer 25, the inclined area IA inclined with respect to the (0001) plane is formed between the terraces T adjacent to the lateral direction as described above. The area outside the inclined area IA that is held up and down by the platform T is called the platform area TA. The film thickness of the p-type cladding layer 25 includes the plateau area TA and the inclined area IA, and is adjusted in the range of 20 nm˜200 nm, for example.

As schematically shown in FIG. 20 , in the p-type cladding layer 25 , through the mass movement of Ga from the plateau area TA to the inclined area IA, in the inclined area IA, the AlN molar ratio is lower than that in the plateau area TA. The third Ga enrichment area 25a.

The AlN molar ratio of the terrace area TA of the p-type cladding layer 25 is 51% or more, which is set within a range that is less than the AlN molar ratio of the terrace area TA of the electron barrier layer 23 . Furthermore, the AlN molar ratio of the Ga-enriched p-type region 25a of the p-type cladding layer 25 is set to be less than the AlN molar ratio of the Ga-rich EB region 23a of the electron barrier layer 23 .

Moreover, the AlN molar ratio of the plateau region TA of the p-type cladding layer 25 is within the above range, and is set to be more than 1%, preferably 2, compared with the AlN molar ratio of the Ga-enriched p-type region 25a. % or more, more preferably 4% or more, set at a high level. In order to sufficiently ensure the localized effect of carriers in the Ga-enriched p-type region 25a, although the difference in AlN molar ratio between the second Ga-enriched region 25a in the p-type cladding layer 25 and the plateau region TA is set to 4-5 % or more is preferred, but at about 1 to 2%, the localized effect of the carrier can be expected.

As a preferred embodiment, in the Ga-enriched EB region 23a of the electron barrier layer 23, the AlN molar ratio that dominates the existence of the AlN molar ratio is more than 20% higher than the AlN molar ratio in the quasi-stable well region, and the AlGaN composition ratio becomes The first quasi-stable EB field composed of p-type quasi-stable AlGaN with an integer ratio of Al _m Ga _12-m N _{12 and} AlN molar fraction of Xe0 (=m/12) is the same in the p-type cladding layer 25 In the Ga-enriched p-type region 25a, the AlGaN composition ratio is dominated by Al iGa _{12-i N 12} whose composition ratio becomes an integer ratio, and the AlN molar ratio is Xp0 (=i/12), which is less than that of the electron barrier layer 23 . The first quasi-stable p-type region composed of AlN molar ratio Xe0 p-type quasi-stable AlGaN in the first quasi-stable EB region. When the electron barrier layer 23 is the same as the electron barrier layer 23 of the light-emitting element 1 of the first embodiment, the integer m is 8, 9, or 10, which is the same as the electron barrier of the light-emitting element 1 of the second or third embodiment. When the layers 23 are the same, the integer m is 8 or 9. The integer i is 6, 7, or 8 and satisfies i<m. Therefore, when the integer m is 8, the integer i is 6 or 7.

Furthermore, as a preferred embodiment, in the Ga-enriched p-type region 25a of the p-type cladding layer 25, the above-mentioned AlGaN composition ratio (Al _i Ga _12-i N ₁₂ , i=6˜8) is formed, and the AlN molybdenum In the first quasi-stable p-type region where the ear fraction is Xp0 (=i/12), the average AlN molar fraction Xpa of the p-type cladding layer 25 is adjusted to be (i+0.24)/12≦Xpa <(i+1)/12 is preferred. The average AlN molar ratio of the plateau region TA of the p-type cladding layer 25 (when forming the Al-rich p-type region described later, the Al-rich p-type region is excluded) is the same as the average AlN of the p-type cladding layer 25 The mole fraction Xpa is similar. Therefore, the difference in molar ratio between the Ga-enriched p-type region 25a of the p-type cladding layer 25 and the AlN molar ratio of the plateau region TA can be ensured to be about 2% or more. However, even if the average AlN molar fraction Xpa of the p-type cladding layer 25 exceeds the range of (i+0.24)/12≦Xpa<(i+1)/12, as long as the inclination of the p-type cladding layer 25 The Ga-enriched p-type domain 25a that can locally exist in the domain IA is formed, and in the range of about 51% to 75%, AlN in the Ga-enriched EB domain 23a corresponding to the electron barrier layer 23 can be obtained Arbitrary value of molar fraction Xe0.

Next, a method of growing the p-type cladding layer 25 will be briefly described. In the formation of the p-type cladding layer 25, in the same manner as the n-type cladding layer 21 and the electron barrier layer 23 described in the first embodiment, under the growth conditions that are easy to express the above-mentioned multi-stage terrace, The p-type cladding layer 25 is grown with the AlN molar fraction Xpa of the p-type cladding layer 25 as a target value.

The average AlN molar fraction Xpa of the p-type cladding layer 25 is in the Ga-enriched p-type region 25a of the p-type cladding layer 25 when the first quasi-stable p-type region of the AlN molar ratio Xp0 is formed , set within the range of Xp0+2%≦Xpa<Xp0+8.33%.

In the fourth embodiment, when the growth temperature of the p-type cladding layer 25 is T5, the relationship between the growth temperature T3 of the electron barrier layer 23 and the growth temperature T4 of the p-type connecting layer is, for example, 1050° C. to 1170° C. Within the range of °C, it is preferable to satisfy the relationship shown by the following formula (3). T3>T5>T4 (3)

Furthermore, when the growth temperature T5 of the p-type cladding layer 25 is the AlN molar ratio Xp0 in the first quasi-stable p-type region is 66.7%, preferably above 1100°C, the AlN molar in the first quasi-stable p-type region is When the fraction Xp0 is 58.3% or 50%, it is better to be above 1050°C.

As an example of growth conditions other than the growth temperature for promoting the mass transfer of Ga of the p-type cladding layer 25, when the growth temperature T5 is 1080°C, the flow ratio (V/III) of the source gas is set to 1000 to 6000, and The growth rate is preferably about 100 nm/h.

The above-mentioned growth temperatures T1 to T5 of the n-type cladding layer 21, the active layer 22 (well layer 220, the barrier layer 221), the electron barrier layer 23, the p-type connecting layer 24, and the p-type cladding layer 25 will be satisfied. An example of formulae (1A), (2) and (3) is shown below. T1=T2=1080℃, T3=1150℃, T4=980℃, T5=1080℃

An example of the above-mentioned growth temperature T5 is applied to the AlN molar fraction Xp0 of the first quasi-stable p-type region in the Ga-enriched p-type region 25a of the p-type cladding layer 25 shown below. Xp0=50%, 58.3%, 66.7%

As an example, the acceptor impurity concentration of the p-type cladding layer 25 is preferably about 1.0×10 ¹⁶ to 1.0×10 ¹⁸ cm ^-3 . However, the acceptor impurity concentration does not necessarily need to be uniformly controlled in the vertical direction with respect to the film thickness of the p-type cladding layer 25 .

Furthermore, as a preferred embodiment of the p-type cladding layer 25, in the p-type cladding layer 25, at the edge portion of the plateau region TA adjacent to the inclined region IA, the uniformity of the p-type cladding layer 25 The AlN molar fraction Xpa is used as a reference, and it is also possible to form an Al-rich p-type region with a high AlN molar fraction locally.

Furthermore, as a preferred embodiment of the p-type cladding layer 25, when the Al-enriched p-type region is formed in the plateau region TA of the p-type cladding layer 25, the Ga-enriched p-type region 25a dominates the p-type region 25a. In addition to the first quasi-stable p-type domain formed by the p-type quasi-stable AlGaN of Al iGa _{12-i N 12} whose AlGaN composition ratio is an integer ratio, in the Al-rich p-type domain, the dominant AlGaN composition ratio is The second quasi-stable p-type region is formed by the p-type quasi-stable AlGaN of the integer ratio of Al _i+1 Ga _11-i N ₁₂ . At this time, the adjustment range of the average AlN molar ratio Xpa of the p-type cladding layer 25 is narrower than the above-mentioned preferred range (the lower limit is (i+0.24)/12), and the AlN molar ratio Xpa is adjusted It is within the first appropriate range of (i+0.5)/12<Xpa<(i+1)/12, and more preferably adjusted to be (i+0.5)/12<Xpa≦ (i+0.9)/12. 2 within the appropriate range.

In the above-described preferred embodiment, by forming the Ga-rich p-type region 25a and the Al-rich p-type region as the first and second quasi-stable p-type regions with high stability, respectively, it is possible to further suppress crystal growth caused by The variation of mixed crystal molar ratio such as device drift, the Ga-enriched p-type region 25a where carriers are locally present in the p-type cladding layer 25, corresponds to the first quasi-stable p-type region used. The AlN molar ratio is stably formed. As a result, in the p-type cladding layer 25 , the current flows preferentially and stably into the Ga-enriched p-type region 25 a , and further, the characteristic variation of the light-emitting element 1 can be suppressed.

The light-emitting element 1 of the fourth embodiment described above is the electron barrier layer 23 and the p-type cladding layer 25 , and has a surface that forms a multi-stage terrace parallel to the (0001) plane of the main surface 11 a of the sapphire substrate 11 . , between the terraces T adjacent to the lateral direction, an inclined area IA inclined to the (0001) plane is formed, and in the inclined area IA of the electron barrier layer 23, a Ga with a lower molar fraction of AlN is formed than the terrace area TA The EB-enriched region 23a is characterized by forming a Ga-enriched p-type region 25a with a lower AlN molar ratio than the plateau region TA in the inclined region IA of the p-type cladding layer 25 .

By virtue of this feature, the light-emitting element 2 of the fourth embodiment can be implanted in the p-type region 25a due to the localization of carriers (holes) generated in the Ga-enriched p-type region 25a, as schematically shown in FIG. 21 . The holes (h+) in the cladding layer 25 (p-clad) are also directly implanted in the inclined area IA, or in the diffusion platform area TA to reach the inclined area IA. Moreover, in the first Ga-enriched region 23a, the localized existence of carriers (holes) is also generated, and the holes implanted in the electron barrier layer 23 are from the inclined region of the p-type cladding layer 25. The IA is also directly implanted in the inclined area IA of the electron barrier layer 23 . Therefore, when there is no p-type cladding layer 25, the p-type connecting layer 24 will be implanted into the terrace area TA of the electron barrier layer 23 of the thin film, and directly reach a part of the holes of the terrace area TA of the well layer 22, from p The plateau area TA of the type cladding layer 25 is transparently guided into the inclined area IA, and reaches the inclined area IA of the well layer 22 through the inclined area IA of the electron barrier layer 23 . As a result, the reduction of the internal quantum efficiency and the generation of double emission peaks can be further suppressed. However, in FIG. 21 , as in FIG. 5 , ☆ (star) indicates a local presence center within the inclined region IA of the well layer, and ● (black circle) indicates a non-luminescent recombination center.

[Other Embodiments] Hereinafter, modifications of the above-described first to fourth embodiments will be described.

(1) In the above-described first to fourth embodiments, the active layer 22 is assumed to alternately stack two or more well layers 220 made of an AlGaN-based semiconductor, and one made of an AlGaN-based semiconductor or an AlN-based semiconductor. In the case where the multiple quantum well structure of the barrier layer 221 is composed of more than one layer, the active layer 22 and the well layer 220 are only a single quantum well structure of one layer, and the structure without the barrier layer 221 (quantum barrier layer) is also Can. For the related single quantum well structure, it is also clear that the effects of the n-type cladding layer 21, the electron barrier layer 23, etc., which are used in the above-described embodiments, can be exerted.

(2) In the above-mentioned embodiments, as an example of the growth conditions of the n-type cladding layer 21, it is explained that the supply amount and flow rate of the raw material gas or the carrier gas used in the organic metal compound vapor phase growth method correspond to the formation of the n-type cladding layer. For the cladding layer 21, the average AlN molar ratio of the entire n-type AlGaN layer is set. That is, when the average AlN molar ratio of the entire n-type cladding layer 21 is set to a constant value in the vertical direction, the supply amount and flow rate of the above-mentioned source gas and the like are assumed to be controlled to be constant. However, the supply amount and flow rate of the above-mentioned raw material gas and the like are not necessarily controlled to be constant.

(3) In each of the above-described embodiments, the shape of the first region R1 and the p-electrode 26 in plan view is taken as an example, and the shape of a comb shape is adopted, but the shape of the plane view is not limited to the comb shape. In addition, a plurality of first regions R1 may exist, and the shape in plane view of each of the second regions R2 surrounded by one may be sufficient.

(4) In the above-mentioned embodiments, although the sapphire substrate 11 whose main surface has an off-angle with respect to the (0001) plane is used as an example, and the surface of the AlN layer 12 is used as the base material portion 10 showing a multi-stage terrace, The magnitude of the off-angle or the direction of setting the off-angle (specifically, the direction of the inclined (0001) plane, such as the m-axis direction or the a-axis direction, etc.) is set on the surface of the AlN layer 12, showing a multi-segment platform, as long as The growth start point for forming the layered region 21a can be arbitrarily determined.

(5) In the above-described embodiments, as the light-emitting element 1, the light-emitting element 1 including the base material portion 10 including the sapphire substrate 11 is exemplified as shown in FIG. 1 . A part or all of the layers in the base material portion 10) are removed by lift-off or the like. Furthermore, the substrate constituting the base material portion 10 is not limited to a sapphire substrate. [Industrial Availability]

The present invention is applicable to a nitride semiconductor ultraviolet light-emitting element formed by an AlGaN-based semiconductor having a sphalerite structure, an n-type layer, an active layer, and a p-type layer, which are laminated on a light-emitting element structure portion in the vertical direction.

1: Nitride semiconductor ultraviolet light-emitting element 10: Substrate part 11: Sapphire substrate 11a: The main surface of the sapphire substrate 12: AlN layer 20: Light-emitting element structure 21: n-type cladding layer (n-type layer) 21a: Layered field (n-type layer) 21b: n-type body field (n-type layer) 22: Active layer 220: Well Layer 220a: Ga-enriched well field 221: Barrier Layer 221a: Ga enrichment barrier field 23: Electronic barrier layer (p-type layer) 23a:Ga-enriched EB field 24: p-type connection layer (p-type layer) 25: p-type cladding layer (p-type layer) 25a: Ga-enriched p-type domain 26:p electrode 27:n electrode 100: Substrate 101: AlGaN-based semiconductor layer 102: Templates 103: n-type AlGaN-based semiconductor layer 104: Active layer 105: p-type AlGaN-based semiconductor layer 106: p-type connection layer 107:n electrode 108:p electrode BL: The Boundary Line Between the 1st Domain and the 2nd Domain IA: Inclined Field R1: Domain 1 R2: Domain 2 T: platform TA: Platform field

[ Fig. 1 ] A diagram schematically showing the sphalerite crystal structure of AlGaN. [ Fig. 2] Fig. 2 is a plan view showing the positional relationship between each position of the A plane and each position of the B plane viewed from the c-axis direction of the sphalerite crystal structure shown in Fig. 1 . [ Fig. 3] Fig. 3 schematically shows the arrangement of Al and Ga in each of the A3 face and the B3 face of five combinations of AlGaN composition ratios expressed as integer ratios. [ Fig. 4] Fig. 4 is a diagram schematically illustrating the behavior of carriers in a well layer and an electron barrier layer of a conventional nitride semiconductor ultraviolet light emitting device. [ Fig. 5] Fig. 5 is a diagram schematically illustrating the behavior of carriers in the well layer and the electron barrier layer of the nitride semiconductor ultraviolet light emitting device according to the second feature of the present invention. [ Fig. 6] Fig. 6 is a cross-sectional view of a main part schematically showing an example of the structure of the nitride semiconductor ultraviolet light-emitting element according to the first to third embodiments. [ Fig. 7] Fig. 7 is a diagram schematically showing a change in the molar ratio of AlN in the Ga-enriched n-type region and the Al-enriched n-type region accompanying the mass shift of Ga in the n-type cladding layer. [ Fig. 8] Fig. 8 is a cross-sectional view of a main part schematically showing an example of the laminated structure of the active layer of the nitride semiconductor ultraviolet light emitting device shown in Fig. 6 . [Fig. 9] shows the emission wavelength of the quantum well structure formed by the AlGaN well layer and the AlGaN barrier layer when the AlN molar fraction of the Ga-enriched well region 220a is 50%, and the film thickness of the well layer and the barrier layer. Graph of AlN molar ratio relationship. Fig. 10 shows the emission wavelength of the quantum well structure formed by the AlGaN well layer and the AlGaN barrier layer when the AlN molar ratio of the Ga-enriched well region 220a is 41.7%, and the film thickness of the well layer and the barrier layer. Graph of AlN molar ratio relationship. Fig. 11 shows the emission wavelength of the quantum well structure formed by the AlGaN well layer and the AlGaN barrier layer when the AlN molar fraction of the Ga-enriched well region 220a is 33.3%, and the film thickness of the well layer and the barrier layer. Graph of AlN molar ratio relationship. 12 is a graph showing the relationship between the emission wavelength of the quantum well structure formed by the GaN well layer and the AlGaN barrier layer, the film thickness of the well layer, and the AlN molar ratio of the barrier layer. [ Fig. 13] Fig. 13 is a plan view schematically showing an example of the structure of the nitride semiconductor ultraviolet light emitting element shown in Fig. 6 as viewed from the upper side of Fig. 6 . 14 is an SEM image showing the main part of the AlN molar ratio measurement section of the sample piece A by the CL method. 15 is an SEM image showing the main part of the AlN molar ratio measurement section of the sample piece B by the CL method. [ Fig. 16] Fig. 16 is a diagram showing the first and second CL spectra on five Y-coordinates on the measurement cross section of the sample piece A shown in Fig. 14 . [ Fig. 17] Fig. 17 is a diagram showing the third and fourth CL spectra on the four Y-coordinates of the upper and lower parts of the measurement cross section of the sample piece B shown in Fig. 15 . [ Fig. 18] Fig. 18 is a diagram showing fifth and sixth CL spectra on five Y-coordinates of the upper portion of the measurement cross section of the sample piece B shown in Fig. 15 . [ Fig. 19] Fig. 19 is a cross-sectional view of a main part schematically showing an example of the structure of the nitride semiconductor ultraviolet light emitting element according to the fourth embodiment. [ Fig. 20] Fig. 20 is a cross-sectional view of the main part schematically showing an example of a laminated structure including the main part of the active layer of the nitride semiconductor ultraviolet light emitting element shown in Fig. 19 . 21 is a diagram schematically illustrating the behavior of carriers in a well layer, an electron barrier layer, and a p-type cladding layer of the nitride semiconductor ultraviolet light-emitting element of the fourth embodiment. [ Fig. 22] Fig. 22 is a cross-sectional view of a main part schematically showing an example of a device structure of a general ultraviolet light emitting diode. [ Fig. 23 ] A HAADF-STEM image showing the cross-sectional structure in the n-type cladding layer, the active layer, and the electron barrier layer of the conventional nitride semiconductor ultraviolet light emitting device.

1: Nitride semiconductor ultraviolet light-emitting element

10: Substrate part

11: Sapphire substrate

11a: The main surface of the sapphire substrate

12: AlN layer

20: Light-emitting element structure

21: n-type cladding layer (n-type layer)

21a: Layered field (n-type layer)

21b: n-type body field (n-type layer)

22: Active layer

220: Well Layer

221: Barrier Layer

23: Electronic barrier layer (p-type layer)

24: p-type connection layer (p-type layer)

26:p electrode

27:n electrode

R1: Domain 1

R2: Domain 2

Claims (11)

A nitride semiconductor ultraviolet light emitting element, which is a nitride semiconductor ultraviolet light emitting element formed by an AlGaN-based semiconductor having a zinc blende structure, an n-type layer, an active layer, and a p-type layer, which are laminated on a light-emitting element structure portion in the upper and lower directions. The device is characterized in that the n-type layer is composed of an n-type AlGaN-based semiconductor, and the active layer disposed between the n-type layer and the p-type layer has one or more layers composed of an AlGaN-based semiconductor. The quantum well structure of the well layer, the p-type layer is composed of p-type AlGaN-based semiconductor, the n-type layer, the active layer and the semiconductor layers in the p-type layer are formed parallel to the (0001) plane The epitaxial growth layer on the surface of the multi-segment terrace, each semiconductor layer in the active layer respectively has a sloping area that connects the adjacent terraces of the multi-segment terrace inclined with respect to the (0001) plane, and the above-mentioned sloping area. In addition to the platform domain, the n-type layer has a local AlN low molar layer domain that is dispersed in the n-type layer as well, and the n-type bulk domain other than the layer domain, which is the same as the n-type domain. Each extending direction of the layered region on the first plane perpendicular to the upper surface of the layer has a portion inclined to the intersection of the upper surface and the first plane of the n-type layer, and the integer n is 5, 6, 7. or 8. In the aforementioned layered region, there is a Ga _- enriched n-type region including an n-type _AlGaN region with an AlGaN composition ratio that is an integer ratio, and within the aforementioned _n -type bulk region , there is an n-type AlGaN domain containing AlGaN with an integer composition ratio of Aln ₊ 1Ga11 _{- nN12} , an Al-enriched n-type domain with a high local AlN molar ratio, the average AlN of the aforementioned n-type layer The molar ratio Xna is in the range of (n+0.5)/12<Xna<(n+1)/12, and in the above-mentioned inclined region of the above-mentioned well layer, the AlN molar ratio is locally higher than that of the above-mentioned well layer. In the aforementioned platform area, the AlN molar ratio is low in the Ga-enriched well area. The nitride semiconductor ultraviolet light emitting device according to claim 1, wherein the average AlN molar fraction Xna of the n-type layer is (n+0.9)/12 or less. The nitride semiconductor ultraviolet light emitting device according to claim 1 or 2, wherein the p-type layer has electrons formed on the upper surface side of the uppermost layer of the one or more well layers as the lowermost layer in the p-type layer. The barrier layer, the electron barrier layer respectively has an inclined region inclined with respect to the (0001) plane between adjacent platforms connecting the multi-segment platforms, and a platform region other than the inclined region, the integer m is 8, 9 Or 10, in the aforementioned inclined region of the aforementioned electron barrier layer, there is a p-type AlGaN region including AlGaN whose composition ratio is an integer ratio to become _{AlmGa12 - mN12} , and local AlN mol fraction is low in Ga enrichment In the EB field, the average AlN molar fraction Xea of the electron barrier layer is in the range of (m+0.24)/12≦Xea<(m+1)/12. The nitride semiconductor ultraviolet light emitting device according to claim 3, wherein, in the plateau region of the electron barrier layer, there is an Al-enriched EB region with a high AlN molar fraction locally, and when the integer m is 8 or 9 , the aforementioned Al-enriched EB field includes the p-type AlGaN field whose AlGaN composition ratio is an integer ratio and becomes Al _m+1 Ga _11-m N ₁₂ , and the average AlN molar fraction Xea of the aforementioned electron barrier layer becomes (m+0.5)/12<Xea<(m+1)/12. The nitride semiconductor ultraviolet light emitting device according to claim 3 or 4, wherein the electron barrier layer has an average AlN molar fraction Xea of (m+0.9)/12 or less. A nitride semiconductor ultraviolet light emitting element, which is a nitride semiconductor ultraviolet light emitting element formed by an AlGaN-based semiconductor having a zinc blende structure, an n-type layer, an active layer, and a p-type layer, which are laminated on a light-emitting element structure portion in the upper and lower directions. The device is characterized in that the n-type layer is composed of an n-type AlGaN-based semiconductor, and the active layer disposed between the n-type layer and the p-type layer has one or more layers composed of an AlGaN-based semiconductor. The quantum well structure of the well layer, the p-type layer is composed of p-type AlGaN-based semiconductor, the n-type layer, the active layer and the semiconductor layers in the p-type layer are formed parallel to the (0001) plane The epitaxial growth layer on the surface of the multi-segment platform, the semiconductor layers in the active layer and the electron barrier layer respectively have an inclination with respect to the (0001) plane connecting the adjacent platforms of the multi-segment platform. The above-mentioned n-type layer has a localized AlN low-molar layered domain that exists uniformly dispersed in the above-mentioned n-type layer, and the above-mentioned n-type bulk domain other than the above-mentioned layered domain , each extending direction of the layered region on the first plane orthogonal to the upper surface of the n-type layer has a portion inclined to the intersection of the upper surface of the n-type layer and the first plane, the p The type layer has, as the lowermost layer in the aforementioned p-type layer, an electron barrier layer formed on the upper surface side of the uppermost layer of the aforementioned one or more well layers, the integer m is 8 or 9, and the aforementioned electron barrier layer is In the oblique field, there are p-type AlGaN fields including _{AlmGa12 - mN12} whose composition ratio is an integer ratio, and Ga-enriched EB fields with low AlN molar fraction locally, in the aforementioned electron barrier layer. In the platform field, there are p-type AlGaN fields including Alm ₊ 1Ga11 _{- mN12} whose composition ratio is an integer ratio, Al-enriched EB fields with high local AlN molar ratio, and one of the aforementioned electron barrier layers. The average AlN molar ratio Xea is in the range of (m+0.5)/12<Xea<(m+1)/12, and in the above-mentioned inclined region of the above-mentioned well layer, there is an AlN molar ratio locally higher than the above-mentioned The aforementioned plateau area of the well layer is a Ga-rich well area with a low AlN molar ratio. The nitride semiconductor ultraviolet light emitting device according to claim 6, wherein the electron barrier layer has an average AlN molar fraction Xea of (m+0.9)/12 or less. The nitride semiconductor ultraviolet light-emitting element according to claim 6 or 7, wherein the integer n is 5, 6, 7, or ₈ , and in the aforementioned layered region, there is AlGaN whose composition ratio is an integer ratio and becomes _{AlnGa12 -n} N ₁₂ is the Ga-rich n-type region of the n-type AlGaN region, and the average AlN molar fraction Xna of the n-type layer becomes (n+0.24)/12<Xna<(n+1)/12 within the range. The nitride semiconductor ultraviolet light emitting device according to any one of claims 1 to 8, wherein the active layer has a multiple quantum well structure including two or more of the well layers, A barrier layer made of an AlGaN-based semiconductor exists between the well layers of the two layers. The nitride semiconductor ultraviolet light emitting device according to claim 9, wherein the barrier layer is made of an AlGaN-based semiconductor, and each has an inclination with respect to the (0001) plane between adjacent terraces connecting the multi-stage terraces. areas, and platform areas other than the aforementioned inclined areas, In the aforementioned inclined region of the aforementioned barrier layer, there is a Ga-enriched barrier region where the AlN molar ratio is locally lower than that of the aforementioned AlN molar ratio of the aforementioned plateau region of the aforementioned barrier layer. The nitride semiconductor ultraviolet light-emitting device according to any one of claims 1 to 10, further comprising a base material portion comprising a sapphire substrate, The sapphire substrate has a main surface inclined only by a specific angle with respect to the (0001) plane, and above the main surface, the light-emitting element structure portion is formed, Each semiconductor layer from the main surface of the sapphire substrate to the contact layer of the p-type layer is an epitaxial growth layer having a surface parallel to the (0001) plane and forming a multi-stage terrace.

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