TW201432937A - Led element - Google Patents

Abstract

Provided is an LED element that ensures horizontal current spreading within an active layer, improving light-emission efficiency, without causing problems due to lattice mismatch in an n-type semiconductor layer adjacent to said active layer. This LED element, which is obtained by inducing c-axis growth of nitride semiconductor layers on top of a support substrate, has the following: a first semiconductor layer comprising an n-type nitride semiconductor a current-diffusion layer an active layer comprising a nitride semiconductor and a second semiconductor layer comprising a p-type nitride semiconductor. The current-diffusion layer contains a heterojunction between a third semiconductor layer comprising InxGa1 - xN (with 0 < x <= 0.05) and a fourth semiconductor layer comprising n-Aly1Gay2Iny3N (with 0 < y1 < 1, 0 < y2 < 1, 0 <= y3 <= 0.05, and y1+y2+y3 = 1), said third semiconductor layer being between 10 and 25 nm thick, inclusive.

Description

LED component

The present invention relates to LED elements, and more particularly to LED elements constructed of nitride semiconductors.

In the LED element using a nitride semiconductor, a semiconductor layer structure (laminated semiconductor substrate) is formed by epitaxial growth on a sapphire substrate, as represented by a blue light-emitting diode. Such a technique is disclosed, for example, in Patent Document 1 and Patent Document 2 which will be described later.

Patent Document 1 discloses an n-type contact layer formed of gallium nitride (GaN) and an n-type cladding layer made of n-AlGaN, which are sequentially laminated on a sapphire substrate as an n-type nitride semiconductor. An LED composed of an active layer made of n-InGaN, a p-type cladding layer made of p-AlGaN, and a p-type contact layer made of p-GaN. The active layer is realized using a single quantum well structure or a multiple quantum well structure.

Then, a buffer layer made of GaN, AlGaN, or AlN is formed between the sapphire substrate and the n-type contact layer. The n-InGaN forming the active layer is doped with a donor impurity such as Si or Gc and/or an acceptor impurity such as Zn or Mg.

Patent Document 2 discloses that in a laminated semiconductor in which an LED is formed, a GaN layer having a larger crystal lattice parameter and a plane orientation aligned with the c-axis direction is grown on AlN having a plane orientation aligned with the c-axis direction. The contents of the n-AlGaN layer having a smaller lattice parameter, the active layer having a multi-quantum well structure, and the p-AlGaN layer are sequentially formed thereon.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 10-93138

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2005-209925

A nitride semiconductor such as GaN or AlGaN has a wurtzite crystal structure (hexagonal crystal structure). The surface of the wurtzite crystal structure is represented by a 4 index (hexagonal crystal index), and the basic planes indicated by a1, a2, a3, and c are used to indicate the crystal plane and orientation. The basic vector c extends in the [0001] direction, which is called the "c-axis". The plane perpendicular to the c-axis is called "c-plane" or "(0001) plane".

When a semiconductor element is produced using a nitride semiconductor, a substrate having a c-plane substrate on its main surface is used as a substrate for crystal growth of a nitride semiconductor. Actually, the undoped GaN layer is grown on the substrate, and the n-type nitride semiconductor layer is grown in the upper layer.

Figure 7 is a diagram showing the outline of the construction of the prior LED element 90. Sectional view. Furthermore, in the following figures, the actual size ratio does not necessarily coincide with the size ratio on the drawing.

The LED element 90 is attached to the upper layer of the support substrate 11 such as sapphire, and has, for example, an undoped layer 13 in which an undoped GaN layer is formed with a film thickness of 3 μm, and an upper layer, for example, a film thickness of 1.5 μm to form an n-AlGaN layer. The n-type cladding layer 15. Further, the LED element 90 is attached to the upper layer of the n-type cladding layer 15 to alternately laminate, for example, InGaN having a thickness of 2 nm which constitutes a quantum well layer and AlGaN having a thickness of 5 nm which constitutes the barrier layer, thereby forming MQW (Multi-quantum Well) : The active layer 17 of a multiple quantum well). Further, the LED element 90 is provided on the upper layer of the active layer 17, and has, for example, a p-type cladding layer 19 formed of p-AlGaN, and a P-type contact layer 21 formed of a p+-GaN layer on the upper layer. Further, the LED element 90 has a final barrier layer formed of AlGaN between the active layer 17 and the p-type cladding layer 19 as needed.

Here, the AlGaN-based lattice parameter constituting the n-type cladding layer 15 is smaller than the GaN of the undoped layer 13 constituting the lower layer. Therefore, tensile stress 81 due to lattice mismatch occurs in the n-type cladding layer 15. Further, the arrow indicated by the tensile stress 81 indicates the orientation of the stress. The tensile stress 81 increases with the increase in the film thickness of the n-type coating layer 15. When the thickness exceeds a certain threshold, misalignment is caused by surface roughening, coating, and crystal defects, resulting in luminous efficiency. reduce.

On the other hand, when the film thickness of the n-type cladding layer 15 is too thin, when a voltage is applied between the power supply terminal (not shown) formed on the upper surface of the p-type contact layer 21 and the n-type cladding layer 15, the power supply terminal is used. Current will pass through The p-type contact layer 21, the p-type cladding layer 19, and the active layer 17 located near the lower side thereof are distributed to the n-type cladding layer 15. Therefore, the current flows only in a portion of one portion of the active layer 17, and the light-emitting region becomes small, resulting in a decrease in luminous efficiency. Further, since a current flows in a part of the active layer 17, a local concentration occurs locally, and a carrier of the carrier layer 17 is uneven, and high luminous intensity cannot be obtained.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an LED element which does not cause a lattice mismatch due to an n-type semiconductor layer adjacent to an active layer, and which ensures current diffusion in a horizontal direction in an active layer and improves luminous efficiency. .

The LED element of the present invention is an LED element formed by growing a nitride semiconductor layer c-axis on a support substrate, and has a first semiconductor layer formed of an n-type nitride semiconductor and a current diffusion layer. The upper layer of the first semiconductor layer is formed; the active layer is formed on the upper layer of the current diffusion layer, and is formed of a nitride semiconductor; and the second semiconductor layer is formed on the upper layer of the active layer, and is p-type a nitride semiconductor; the current diffusion layer has a third semiconductor layer formed of In _x Ga _1-x N (0 < x ≦ 0.05), and n-Al _y Ga _1-y N (0<异1) The heterojunction of the fourth semiconductor layer formed, wherein the thickness of the third semiconductor layer is 10 nm or more and 25 nm or less.

By the heterojunction of the third semiconductor layer formed of In _x Ga _1-x N and the fourth semiconductor layer formed of n-Al _y Ga _1-y N, due to the difference in energy band gap between the two materials, The interface between the two layers forms a bendable region. A two-dimensional electron gas layer having a high degree of horizontal mobility is formed in the band bending region.

Here, if the In ratio of In _x Ga _1-x N is raised to more than 10%, distortion due to the energy band of the piezoelectric electric field is generated, and the luminous efficiency is lowered due to the quantum Stuck effect. This is even if the quantum well layer formed by In _a Ga _1-a N (0<a≦1) and the barrier layer formed by Al _b Ga _1-b N (0<b≦1) are repeated. The same is true for the multi-quantum well structure to achieve the active layer. Here, the ratio of the In composition is a factor that determines the wavelength of the emitted light. In other words, when the In ratio of In _x Ga _1-x N constituting the current diffusion layer and the In _a Ga _1-a N (0<a≦1) constituting the active layer are 10% or less, it can be taken out. The present invention is particularly useful for light, i.e., LED elements having a wavelength of, for example, near 365 nm.

Furthermore, by the film thickness formed by the In _x Ga _1-x N of the third semiconductor layer, In order to construct compared to the quantum well layers formed of quantum well structure is generally much film _x Ga _1-x N of It is thick (for example, about 2 nm) and has a sufficient thickness of 10 nm or more and 25 nm or less. In the general multi-quantum well structure, in order to prevent a decrease in the light-emitting ratio due to the quantum Stark effect, the film thickness of In _x Ga _1-x N is set to about 2 nm, and even if it is thick, it is set to 3 nm or less. .

However, in the LED element of the present invention, the film thickness of In _x Ga _1-x N constituting the current diffusion layer is 10 nm or more and 25 nm or less. Thus, by increasing the film thickness, the almost flat band region formed by In _x Ga _1-x N can be increased, and the capacity for securing electrons can be increased. Between the accumulation of electrons in this region, electrons cannot exceed the barrier formed by n-Al _y Ga _1-y N. Between, the two-dimensional electron gas moves in a direction parallel to the interface, so the electrons will spread in the horizontal direction. That is, in the stage where electrons are sufficiently diffused in the horizontal direction, electrons may exceed n-Al _y Ga _1-y N in a stage in which a sufficient amount of electrons are accumulated in the band bending region and the nearly flat band region. The barrier moves to the side of the p-layer. In other words, the current is temporarily diffused in the horizontal direction until the current flows from the p-layer side to the n-layer side. Thereby, since the current flowing in the active layer is diffused in the horizontal direction, the active layer can be entirely illuminated, and the luminous efficiency can be improved.

On the other hand, the inventors of the present invention have found that when the film thickness of In _x Ga _1-x N is made thicker than 25 nm, for example, 30 nm, problems such as crystal defects are remarkable, and light output is lowered. That is, the film thickness of In _x Ga _1-x N is preferably set to be less than or equal to the thickness of the film which does not cause crystal defects.

Therefore, by setting the film thickness of In _x Ga _1-x N to 10 nm or more and 25 nm or less as described above, it is possible to obtain an effect of improving the light output compared to the conventional LED element.

Further, it has been found by the inventors' intensive research that it is possible to secure a Si doping concentration of n-Al _y Ga _1-y N to 1 × 10 ¹⁸ /cm ³ or more and 5 × 10 ¹⁸ /cm ³ or less. This light output enhances the effect. For example, the Si doping concentration is set to be seen / cm value of 5 × 10 ¹⁷ / cm ^3, etc. than 1 × 10 ^{18 3} less, the unevenness generated within the active layer of the carrier along the carrier absolutely insufficient, other On the other hand, when the ratio of 9 × 10 ¹⁸ /cm ³ or the like is set to a value higher than 5 × 10 ¹⁸ /cm ³ , a decrease in efficiency occurs, and neither of them can obtain a high light output.

Therefore, by setting the film thickness of In _x Ga _1-x N to 10 nm or more and 25 nm or less, the Si doping concentration of n-Al _y Ga _1-y N is further set to 1 × 10 ¹⁸ /cm ³ or more. When it is 5 × 10 ¹⁸ /cm ³ or less, the effect of improving the light output can be obtained as compared with the previous LED element.

Further, the current diffusion layer may have a structure in which the current diffusion layer has a plurality of heterogeneous connections by stacking the third semiconductor layer and the fourth semiconductor layer.

As such a structure, a plurality of electron wells forming a two-dimensional electron gas layer are also formed according to an interface in which a plurality of heterojunctions are formed. Further, an electron well caused by a plurality of In _x Ga _1-x N having a function of an electron accumulation layer is also formed. Thereby, the effect of current spreading can be further improved.

According to the present invention, since the current can be diffused in the horizontal direction while forming the n-type cladding layer in a film thickness within a range that does not cause crystal defects, an LED element having high luminous efficiency can be realized.

1‧‧‧LED components

3‧‧‧current diffusion layer

11‧‧‧Support substrate

13‧‧‧Undoped layer

15‧‧‧n type coating

17‧‧‧Active layer

19‧‧‧p type coating

21‧‧‧p-type contact layer

30‧‧‧Transmission belt

31‧‧‧Price electronic tape

32‧‧‧Fermien order of InGaN

33‧‧‧Fermien order of AlGaN

41‧‧‧Bend zone formed at the interface between AlGaN and InGan

42‧‧‧ Nearly flat band regions formed by InGaN

81‧‧‧ tensile stress

90‧‧‧LED components

Fig. 1 is a schematic cross-sectional view showing the structure of an LED element of the present invention.

FIG. 2 is a graph showing the relationship between the current flowing through the active layer and the light output obtainable from the LED element when the In composition of In _x Ga _1-x N is changed.

[Fig. 3A] The mode reveals an ideal energy band diagram of the current diffusion layer.

[Fig. 3B] Reflecting the influence of the piezoelectric electric field, the mode reveals the energy band diagram of the current diffusion layer.

[Fig. 3C] Reflecting the interaction of the semiconductor material, the mode reveals the energy band diagram of the conduction band of the current diffusion layer.

Fig. 4 is a graph showing the relationship between the current flowing through the active layer and the light output obtainable from the LED element when the film thickness of In _x Ga _1-x N is changed.

Fig. 5 is a graph showing the relationship between the current flowing through the active layer and the light output obtainable from the LED element when the Si doping concentration of AlGaN is changed.

Fig. 6A is a schematic cross-sectional view showing another structure of an LED element of the present invention.

[Fig. 6B] Reflecting the interaction of the semiconductor material, the mode reveals the energy band diagram of the conduction band of the current diffusion layer of the configuration of Fig. 6A.

Fig. 7 is a schematic cross-sectional view showing the structure of a conventional LED element.

[structure]

Fig. 1 is a schematic cross-sectional view showing the structure of an LED element 1 of the present invention. Incidentally, the same components as those of the LED element 90 shown in FIG. 7 are denoted by the same reference numerals. Moreover, in the following drawings, the actual size ratio does not necessarily match the size ratio on the drawing.

The LED element 1 is additionally provided in comparison with the LED element 90. The current diffusion layer 3 is different. In other words, the LED element 1 is provided on the upper layer of the support substrate 11 such as sapphire, and includes the undoped layer 13 and the n-type cladding layer 15 (corresponding to the "first semiconductor layer"), the current diffusion layer 3, and the active layer. 17. A p-type cladding layer 19 (corresponding to a "second semiconductor layer") and a p-type contact layer 21. Further, similarly to the LED element 90, a final barrier layer (not shown) is provided between the active layer 17 and the p-type cladding layer 19 as needed.

(Support substrate 11)

The support substrate 11 is composed of a sapphire substrate. Further, in addition to sapphire, Si, SiC, GaN, YAG, or the like may be used.

(undoped layer 13)

The undoped layer 13 is formed of GaN. More specifically, it is formed by a low temperature buffer layer made of GaN and a base layer made of GaN on its upper layer.

(n-type coating layer 15)

The n-type cladding layer 15 is composed of n-Al _n Ga _1-n N (0<n<1). Further, as a region contacting the undoped layer 13, a structure including a layer (protective layer) made of n-GaN may be used. At this time, the protective layer is doped with an n-type impurity such as Si, Ge, S, Se, Sn, or Te, and particularly preferably Si is doped.

Further, in the present embodiment, as an example, the n-type cladding layer 15 is formed of n-Al _0.1 Ga _0.9 N.

(active layer 17)

The active layer 17 is formed of, for example, a quantum well layer formed by repeating In _a Ga _1-a N (0<a≦1) and a barrier layer formed of Al _b Ga _1-b N (0<b≦1) A semiconductor layer of a multi-quantum well structure (MQW) is formed. These layers may be used as a non-doped type, and may be doped p-type or n-type.

In the present embodiment, as an example, the quantum well layer in the active layer 17 is made of In _0.04 Ga _0.96 N, and the barrier layer is made of Al _0.06 Ga _0.94 N, and the quantum well layer and the barrier layer are repeated for five cycles. The active layer 17 is formed. In the LED element 1, the number of repetition periods is not limited to five.

(p type coating layer 19)

The p-type cladding layer 19 is composed of, for example, p-Al _c Ga _1-c N (0<c≦1), and is doped with a p-type impurity such as Mg, Be, Zn, or C. In the present embodiment, as an example, the p-type cladding layer 19 is formed by a laminated structure of p-Al _0.3 Ga _0.7 N and p-Al _0.07 Ga _0.93 N. Further, a structure including a layer (protective layer) made of GaN may be used as a region in contact with the p-contact layer 21. At this time, the protective layer is doped with a p-type impurity such as Mg, Be, Zn, or C.

(p-type contact layer 21)

The P-type contact layer 21 is made of, for example, p-GaN. Especially p-type impurities doped with Mg, Be, Zn, C, etc. at high concentration, with p+-GaN layer structure to make.

(current diffusion layer 3)

The current diffusion layer 3 is composed of a layer formed of In _x Ga _1-x N (0 < x ≦ 0.05) (corresponding to "third semiconductor layer"), and n-Al _y Ga _1-y N (0 < y≦1) A heterogeneous junction of the formed layer (corresponding to the "fourth semiconductor layer"). The film thickness of In _x Ga _1-x N constituting the third semiconductor layer is 10 nm or more and 25 nm or less.

[Explanation of the effect of the current diffusion layer 3]

Hereinafter, the state in which the luminous efficiency of the LED element 1 is higher than that of the conventional LED element 90 by the current diffusion layer 3 having the above-described structure will be described with reference to the embodiments.

(Investigation on the In composition of the third semiconductor)

2 is a view showing the In composition of In _x Ga _1-x N (third semiconductor layer) constituting the current diffusion layer 3, that is, the current flowing through the active layer 17 and the light obtained from the LED element 1 when the value of x is changed. A chart of the relationship of the output. Further, for comparison, the data of the previous LED element 90 in which the current diffusion layer 3 is not provided is also described.

When the In composition is 2% or 5%, it is understood that any of the light outputs larger than the previous LED element 90 can be obtained. On the other hand, when the In composition is set to 10%, it is understood that the light output is lowered below the LED element 90. The result is the following.

3A and 3B are diagrams showing the energy band diagram of the current diffusion layer 3. In the following, when the composition of each atom is not observed, the third semiconductor layer is referred to as InGaN, and the fourth semiconductor layer is referred to as AlGaN. However, the ratio of atoms other than the predetermined nitrogen is not 1:1.

Compared to InGaN, AlGaN has a larger band gap. Therefore, as shown in FIG. 3A, the near-flatness caused by InGaN is formed between n-AlGaN constituting the n-type cladding layer 15 and AlGaN of the current diffusion layer 3, irrespective of the influence of the polarization electric field to be described later. Can bring area. Here, the film thickness of InGaN constituting the current diffusion layer 3 is much thicker than the thickness of InGaN (for example, 2 nm) constituting the active layer 17, and is composed of 10 nm or more and 25 nm or less. Therefore, a nearly flat band region is widely formed. .

When the AlGaN crystal constituting the n-type cladding layer 15 is grown on the c-plane of the GaN crystal constituting the undoped layer 13 to form a heterojunction, as described above, the GaN crystal is formed according to the lattice parameter difference. Tensile stress is generated, and piezoelectric polarization occurs in the c-axis direction in the GaN crystal. The internal electric field (piezoelectric electric field) due to the piezoelectric polarization causes a large polarization electric field (piezoelectric electric field) in the c-axis direction perpendicular to the well surface of the InGaN of the current diffusion layer 3 constituting the quantum well layer. ).

Fig. 3B is a mode showing the energy band of the current diffusion layer 3 depicted in consideration of the influence of the piezoelectric electric field. Due to the piezoelectric electric field, the energy band is distorted.

If the distortion of the energy band is increased, the overlap of the wave function of the electron and the hole will be reduced, and the ratio of the electron and the hole will be combined again. Lower, resulting in the so-called quantum Stark effect. The larger the In composition ratio in the tortuous system InGaN, the larger. In FIG. 2, when the In composition is increased to 10%, the light output reduction is remarkable due to the quantum Stuck effect compared to the previous LED element 90 in which the current diffusion layer 3 is not provided.

On the other hand, when the In composition is 2% or 5%, the light output is increased as compared with the previous LED element 90. For this reason, the following contents are conceivable.

As shown in FIG. 3A, the AlGaN-based electronic properties have a larger band gap than InGaN. In FIG. 3A, the conduction band 30, the valence band 31, and the Fermi level 32 of InGaN and the Fermi level 33 of AlGaN are disclosed. Furthermore, in FIG. 3A, the interaction between InGaN and AlGaN is not considered.

The Figure 3C mode reveals the state of the conductive strip 30 that reflects the interaction of the two semiconductor devices. The Fermi level 32 and 33 are equi-positioned with each other. However, due to the discontinuity of the energy band of AlGaN and InGaN, the conduction band of the AlGaN layer close to the p-layer is pulled downward to generate the band bend region 41. In the energy band bending region 41, a two-dimensional electron gas layer having a high horizontal mobility is formed. Further, as described above, since the thickness of the InGaN layer is increased, the nearly flat band region 42 is expanded and a large amount of electrons can be accumulated. Therefore, the band bend region 41 formed at the interface between AlGaN and InGaN and InGaN are formed. When the nearly flat energy band region 42 accumulates electrons, the electrons do not exceed the potential of the AlGaN and exceed the limit. That is, the movement of electrons in the horizontal direction is sought, and as a result, current spreading in the horizontal direction can be realized. That is, the current diffusion layer 3 is realized by AlGaN and InGaN.

From the above, it is understood that the effect of increasing the light output of the LED element 1 can be obtained by setting the In ratio of InGaN to be higher than 0% and 5% or less.

Further, in particular, by increasing the film thickness of InGaN, the current spreading effect can be improved, and the light output can be improved. This point is explained below.

(Investigation on the film thickness of the third semiconductor)

As described above, it is preferable to increase the film thickness of the third semiconductor (InGaN) in the sense that the near-flat energy band region 42 is formed by InGaN. However, due to the difference in lattice parameters between GaN and InGaN, if the film thickness of InGaN is excessively increased, lattice relaxation occurs, and electrons cannot be sufficiently accumulated in the band bending region 41 and the nearly flat band region 42.

Fig. 4 is a graph showing the relationship between the current flowing through the active layer and the light output obtainable from the LED element when the film thickness of InGaN is changed. Furthermore, the In composition was set to 2%. According to FIG. 4, when the film thickness of InGaN is 10 nm, the light output equivalent to that of the previous LED element 90 not including the current diffusion layer 3 can be obtained, and when the thickness of InGaN is 15 nm, 20 nm, or 25 nm, it can be seen that high can be obtained. Previous light output. Further, when the film thickness of InGaN is set to 15 nm, the highest light output can be obtained in a wide range of applied current values.

On the other hand, when the film thickness of InGaN is 30 nm, the light output is lower than that of the previous LED element 90. This system sets the film thickness At 30 nm, crystal defects due to the aforementioned lattice relaxation occur, and the uniformity of the current in the plane is lowered, and as a result, the light output is also lowered.

Further, as shown in FIG. 4, when the film thickness of InGaN is set to 5 nm of less than 10 nm, the light output is lowered to be lower than that of the previous LED element 90. Referring to FIG. 3B, as described above, the reason is that the nearly flat energy band region 42 formed by InGaN is also affected by the piezoelectric electric field, and the ability to accumulate electrons is lowered.

From the above, it is understood that the effect of increasing the light output of the LED element 1 can be obtained by setting the film thickness of InGaN to 10 nm or more and 25 nm or less.

(Review on the Si doping concentration of the fourth semiconductor)

FIG. 5 is a graph showing the relationship between the current flowing in the active layer and the light output that can be obtained from the LED element when the Si doping concentration of the fourth semiconductor (AlGaN) constituting the current diffusion layer 3 is changed. Further, the In composition of InGaN was set to 2%, and the film thickness was set to 15 nm.

According to Fig. 5, the highest light output is exhibited at a Si doping concentration of 3 × 10 ¹⁸ (/cm ³ ). Further, at 1 × 10 ¹⁸ (/cm ³ ), 3 × 10 ¹⁸ (/cm ³ ), and 5 × 10 ¹⁸ (/cm ³ ), it is understood that either of them shows higher light output than the previous LED element 90 ( Refer to Figure 4). In contrast, the case where the Si doping concentration is lower than 1 × 10 ¹⁸ (/cm ³ ) of 5 × 10 ¹⁷ (/cm ³ ), and the case where the Si doping concentration is higher than 5 × 10 ¹⁸ (/cm ³ ) is 9 × 10 ¹⁸ In the case of (/cm ³ ), it is understood that the light output is lower than that of the previous LED element 90 (refer to FIG. 4).

When the Si doping concentration of AlGaN is 5 × 10 ¹⁷ (/cm ³ ), since the Si concentration is absolutely low, unevenness of Si is generated in the active layer 17, resulting in a decrease in light output. On the other hand, when the Si doping concentration of AlGaN is 9 × 10 ¹⁸ (/cm ³ ), heat generation due to current concentration causes a decrease in the probability of recombination of light emission, which causes deterioration of internal light emission efficiency, so that efficiency is lowered. The light output is reduced.

According to the above, it is understood that the light output of the LED element 1 can be further improved by using the Si concentration of the AlGaN constituting the current diffusion layer 3 to be 1×10 ¹⁸ (/cm ³ ) or more and 5×10 ¹⁸ (/cm ³ ) or less. Effect.

[Method of Manufacturing LED Element 1]

Next, a method of manufacturing the LED element 1 of the present invention will be described. In addition, the manufacturing conditions, the film thickness, and the like described in the manufacturing method described later are merely examples, and are not limited to the numerical values.

<Step S1>

First, an undoped layer 13 is formed on the support substrate 11. For example, it is carried out by the following works.

(Preparation of support substrate 11)

When the sapphire substrate is used as the support substrate 11, the c-plane sapphire substrate is cleaned. More specifically, the c-plane sapphire substrate is placed in a treatment furnace of a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus, and hydrogen gas having a flow rate of 10 slm is flowed into the treatment furnace. Put the furnace The internal temperature is raised, for example, to 1,150 °C.

(Formation of undoped layer 13)

Next, a low temperature buffer layer made of GaN is formed on the surface of the support substrate 11 (c-plane sapphire substrate), and a base layer made of GaN is formed on the upper layer. The low temperature buffer layer and the base layer correspond to the undoped layer 13.

A more specific method of forming the undoped layer 13 is as follows, for example. First, the furnace internal pressure of the MOCVD apparatus was set to 100 kPa, and the furnace internal temperature was set to 480 °C. Then, while supplying a nitrogen gas and a hydrogen gas having a flow rate of 5 slm in the processing furnace as a carrier gas, trimethylgallium having a flow rate of 50 μmol/min and ammonia having a flow rate of 250,000 μmol/min were supplied as a raw material gas for 68 seconds. To the inside of the furnace. Thereby, a low temperature buffer layer made of GaN having a thickness of 20 nm was formed on the surface of the support substrate 11.

Next, the furnace temperature of the MOCVD apparatus was raised to 1,150 °C. Then, a nitrogen gas having a flow rate of 20 slm and a hydrogen gas having a flow rate of 15 slm were used as a carrier gas in the treatment furnace, and trimethylgallium having a flow rate of 100 μmol/min and ammonia having a flow rate of 250,000 μmol/min were used as a material gas. Supply for 30 seconds to the furnace. Thereby, a base layer made of GaN having a thickness of 1.7 μm was formed on the surface of the first buffer layer.

<Step S2>

Next, an n-type cladding layer 15 composed of n-Al _n Ga _1-n N (0 < n ≦ 1) is formed on the upper layer of the undoped layer 13.

A more specific formation method of the n-type coating layer 15 is as follows, for example. First, the pressure in the furnace of the MOCVD apparatus was set to 30 kPa. Then, a nitrogen gas having a flow rate of 20 slm and a hydrogen gas having a flow rate of 15 slm were used as a carrier gas in the treatment furnace, and trimethylgallium having a flow rate of 94 μmol/min and a flow rate of 6 μmol/min were used as a material gas. Methyl aluminum, ammonia having a flow rate of 250,000 μmol/min, and tetraethyl decane having a flow rate of 0.025 μmol/min were supplied to the treatment furnace for 30 minutes. Thereby, a high-concentration electron supply layer having a composition of Al _0.06 Ga _0.94 N, a Si concentration of 3 × 10 ¹⁹ /cm ³ and a thickness of 1.7 μm was formed on the upper layer of the undoped layer 13 . That is, by this work, at least the upper region, the n-type cladding layer 15 having a high-concentration electron supply layer having a Si concentration of 3 × 10 ¹⁹ /cm ³ and a thickness of 1.7 μm is formed.

Further, as the n-type impurity contained in the n-type cladding layer 15, bismuth (Si), bismuth (Se), sulfur (S), selenium (Se), tin (Sn), tellurium (Te), or the like can be used. Among these, especially bismuth (Si) is preferred.

<Step S3>

Next, for the upper layer of the undoped layer 13, a third semiconductor layer formed of In _x Ga _1-x N (0 < x ≦ 0.05) is formed, and n-Al _y Ga _1-y N (0< The fourth semiconductor layer formed by y≦1) forms the current diffusion layer 3.

A more specific method of forming the current diffusion layer 3 is, for example, the following Said. First, the furnace internal pressure of the MOCVD apparatus was set to 100 kPa, and the furnace internal temperature was set to 830 °C. Then, a nitrogen gas having a flow rate of 15 slm and a hydrogen gas having a flow rate of 1 slm as a carrier gas in the treatment furnace were used, and trimethylgallium having a flow rate of 10 μmol/min and a flow rate of 12 μmol/min were used as a material gas. The trimethyl indium and the ammonia having a flow rate of 300,000 μmol/min were supplied to the inside of the treatment furnace in 360 seconds. Thereafter, trimethylgallium having a flow rate of 10 μmol/min, trimethylaluminum having a flow rate of 1.6 μmol/min, tetraethylnonane at 0.002 μmol/min, and ammonia having a flow rate of 300,000 μmol/min were supplied to the treatment in 360 seconds. The steps inside the furnace. Thereby, a current diffusion layer 3 made of InGaN having a thickness of 15 nm and n-AlGaN having a thickness of 20 nm was formed.

<Step S4>

Next, in the upper layer of the current diffusion layer 3, a quantum well layer formed by repeating In _a Ga _1-a N (0<a≦1) and Al _b Ga _1-b N (0<b≦1) are formed. The active layer 17 of the multi-quantum well structure formed by the barrier layer formed.

A more specific method of forming the active layer 17 is as follows, for example. First, the furnace internal pressure of the MOCVD apparatus was set to 100 kPa, and the furnace internal temperature was set to 830 °C. Then, a nitrogen gas having a flow rate of 15 slm and a hydrogen gas having a flow rate of 1 slm as a carrier gas in the treatment furnace were used, and trimethylgallium having a flow rate of 10 μmol/min and a flow rate of 12 μmol/min were used as a material gas. The trimethyl indium and the ammonia having a flow rate of 300,000 μmol/min were supplied to the treatment furnace in 48 seconds. Thereafter, trimethylgallium having a flow rate of 10 μmol/min was used, and the flow rate was 1.6 μmol/min of trimethylaluminum, 0.002 μmol/min of tetraethylnonane, and a flow rate of 300,000 μmol/min of ammonia were supplied to the treatment furnace for 120 seconds. Hereinafter, the activity of a 5-cycle multi-quantum well structure caused by a quantum well layer made of InGaN and a barrier layer made of n-AlGaN having a thickness of 7 nm having a thickness of 2 nm is repeated by repeating the two steps. The layer 17 is formed on the upper layer of the current diffusion layer 3.

<Step S5>

Next, on the upper layer of the active layer 17, a p-type cladding layer 19 composed of p-Al _c Ga _1-c N (0 < c ≦ 1) is formed, and a p-contact layer 21 having a high concentration is formed on the upper layer.

More specific formation methods of the p-type cladding layer 19 and the p-contact layer 21 are as follows, for example. First, the furnace pressure in the MOCVD apparatus was maintained at 100 kPa, and a nitrogen gas having a flow rate of 15 slm and a hydrogen gas having a flow rate of 25 slm were used as a carrier gas in the treatment furnace, and the temperature in the furnace was raised to 1,050 °C. Thereafter, trimethylgallium having a flow rate of 35 μmol/min, trimethylaluminum having a flow rate of 20 μmol/min, ammonia having a flow rate of 250,000 μmol/min, and bis(cyclopentadiene) having a flow rate of 0.1 μmol/min were used as a material gas. Magnesium is supplied to the treatment furnace in 60 seconds. Thereby, a hole supply layer having a composition of Al _0.3 Ga _0.7 N having a thickness of 20 nm was formed on the surface of the active layer 17. Thereafter, by changing the flow rate of trimethylaluminum to 9 μmol/min and supplying the material gas for 360 seconds, a hole supply layer having a composition of Al _0.07 Ga _0.93 N having a thickness of 120 nm was formed. The p-type cladding layer 19 is formed by the holes supply layer.

Further, after that, the supply of trimethylaluminum was stopped, and the flow rate of bis(cyclopentadienyl)magnesium was changed to 0.2 μmol/min, and the source gas was supplied for 20 seconds. Thereby, a p-type contact layer 21 made of p-GaN having a thickness of 5 nm was formed.

Further, as the p-type impurity, magnesium (Mg), beryllium (Be), zinc (Zn), carbon (C) or the like can be used.

<Step S6>

Next, the wafers obtained in steps S1 to S5 are subjected to activation treatment. More specifically, it was subjected to an activation treatment at 650 ° C for 15 minutes in a nitrogen atmosphere using an RTA (Rapid Thermal Anneal) apparatus.

Thereafter, when the vertical LED element is realized, after the support substrate 11 is peeled off, an electrode is formed at the place where the support substrate 11 exists to form an n-side electrode. Further, when a horizontal LED element is realized, etching is performed until the n-type semiconductor layer is exposed from the p side, and an n-side electrode is formed. In this case, an electrode such as a transparent electrode may be formed as needed. Thereafter, a power supply terminal or the like is formed on each of the electrodes, and the exposed side surface and the upper surface of the element are required to be covered with an insulating layer having high light transmittance, and the connection to the substrate is performed by wire bonding or the like.

[Other Embodiments]

Hereinafter, other embodiments will be described.

In the LED element 1, a plurality of layers formed of In _x Ga _1-x N (0<x≦0.05) are repeated, and are formed by n-Al _y Ga _1-y N (0<y≦1). The heterogeneous connection of the layers may constitute the current diffusion layer 3 (see FIG. 6A). Further, Fig. 6B is an energy band diagram showing the conduction band of the current diffusion layer 3 of the configuration of Fig. 6A in accordance with Fig. 3C.

With the configuration shown in FIG. 6A, since there are a plurality of energy band bending regions 41 serving as a function of diffusing current in a horizontal direction, and a nearly flat energy band region 42 having a function of accumulating electrons, it is possible to compare with the nearly flat energy band region 42 of the function of accumulating electrons. The structure further enhances the effect of current spreading. Thereby, the light output can be further improved.

1‧‧‧LED components

3‧‧‧current diffusion layer

11‧‧‧Support substrate

13‧‧‧Undoped layer

15‧‧‧n type coating

17‧‧‧Active layer

19‧‧‧p type coating

21‧‧‧p-type contact layer

Claims (3)

An LED element is an LED element formed by growing a nitride semiconductor layer c-axis on a support substrate, and is characterized in that: the first semiconductor layer is made of an n-type nitride semiconductor; and the current diffusion layer is formed. An upper layer of the first semiconductor layer; an active layer formed on the upper layer of the current diffusion layer and formed of a nitride semiconductor; and a second semiconductor layer formed on the upper layer of the active layer and having a p-type nitride The current diffusion layer has a third semiconductor layer formed of In _x Ga _1-x N (0 < x ≦ 0.05) and n-Al _y Ga _1-y N (0 < y ≦ 1) The heterojunction of the formed fourth semiconductor layer, the film thickness of the third semiconductor layer being 10 nm or more and 25 nm or less. The LED element according to the first aspect of the invention, wherein the fourth semiconductor layer has a Si doping concentration of 1 × 10 ¹⁸ /cm ³ or more and 5 × 10 ¹⁸ /cm ³ or less. The LED element according to the first or second aspect of the invention, wherein the current diffusion layer is formed by stacking the third semiconductor layer and the fourth semiconductor layer in an array, and has a plurality of heterogeneous connections. structure.