JP3835225B2 - Nitride semiconductor light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor light emitting device such as a light emitting diode (LED) or a laser diode (LD), and in particular, emits light to a nitride semiconductor light emitting device in which a semiconductor layer structure laminated on a substrate is composed of a nitride semiconductor. It relates to an element.
[0002]
[Prior art]
Nitride semiconductors such as InGaN, AlGaN, and GaN are promising as materials for semiconductor light emitting devices such as LEDs and LDs that emit light in the wavelength region from the ultraviolet to the red region. Currently, blue LEDs and blue-green LEDs made of these nitride semiconductor materials have been put into practical use and are used for displays, signals, and the like.
[0003]
These blue and blue-green light emitting nitride semiconductor LED devices have a double hetero structure, and basically, an n-type contact layer made of n-type GaN and an n-type clad made of n-type AlGaN on a substrate. A layer, an active layer made of n-type InGaN, a p-type cladding layer made of p-type AlGaN, and a p-type contact layer made of p-type GaN are sequentially stacked. The active layer is doped with donor impurities such as Si and Ge and / or acceptor impurities such as Zn and Mg. The emission wavelength of the LED element can be changed from the ultraviolet to the red region by changing the In ratio of InGaN constituting the active layer or changing the type of impurities doped in the active layer.
[0004]
On the other hand, various structures have been proposed for LD elements. For example, Japanese Patent Laid-Open No. 6-21511 discloses a separate confinement type LD element. In this LD element, an active layer made of InGaN having a thickness of 100 angstroms or less is sandwiched between an n-type GaN layer and a p-type GaN layer, and a p-type AlGaN layer is formed on each of the n-type GaN layer and the p-type GaN layer. And an n-type AlGaN layer. In this element, the AlGaN layer functions as an optical confinement layer.
[0005]
[Problems to be solved by the invention]
As for the nitride semiconductor LED element, the light emission output has been improved to a practical level due to the realization of the double hetero structure as described above. However, not only an LED element that exhibits higher light emission output is desirable, but also in the conventional LED element, since the active layer (light emitting layer) is doped with impurities, the half width of the emission spectrum is low. There is a tendency to become wide. When the half-value width of the emission spectrum is wide, the emission color appears white, so when a full color display is produced using such LED elements, for example, the color reproduction area of the color display becomes narrow. It becomes.
[0006]
On the other hand, a nitride semiconductor LD element can be theoretically realized by a double heterostructure having an active layer formed of non-doped InGaN, as described in Japanese Patent Laid-Open No. 6-21511. In reality, the LD element has not oscillated. In particular, as described in this publication, the light emission output should be greatly improved by making the active layer a quantum well structure, but as described above, the laser oscillation has not actually been achieved.
[0007]
Therefore, when the present invention is applied to an LED element, an LED element having a high light emission output and a narrow half-value width of the emission spectrum can be realized, and when applied to an LD element, an LD capable of actual laser oscillation. It is an object of the present invention to provide a nitride semiconductor light emitting device having a novel structure capable of realizing the device.
[0008]
[Means for Solving the Problems]
As a result of intensive studies on a nitride semiconductor light emitting device having a structure in which an active layer is sandwiched between a p-type semiconductor layer and an n-type semiconductor layer, the present inventors have formed an active layer of InGaN and formed it with a quantum well structure (single The light emission from the active layer can be based on InGaN band-to-band light emission, thereby obtaining light emission with a narrow half width, In addition, it has been found that a nitride semiconductor light emitting device that exhibits high light emission output and / or can perform actual laser oscillation can be obtained by providing a specific p-type layer or n-type layer in contact with the active layer. Based on these findings, further research has been conducted and the present invention has been completed.
[0009]
  More specifically, according to the first aspect of the present invention, there is provided an active layer having a quantum well structure having a first and second main surfaces and including a nitride semiconductor containing indium and gallium, A semiconductor multilayer structure having an n-type nitride semiconductor layer provided on a first main surface of the layer and a p-type nitride semiconductor layer provided on a second main surface of the active layer, The first nitride semiconductor layer is provided in contact with the first main surface of the active layer, and includes a first n-type cladding layer made of n-type nitride semiconductor or n-type GaN containing indium and gallium; Provided at a position farther from the active layer than the first n-type cladding layer;Having a larger band gap than the first n-type cladding layer,Andn-type Al _f Ga _1-f N (0 <f <1)And a second n-type cladding layer made of a nitride semiconductor containing p. The p-type nitride semiconductor layer is provided in contact with the second main surface of the active layer, and includes p containing aluminum and gallium. 1. A nitride semiconductor light emitting device comprising: a first p-type cladding layer made of a type nitride semiconductor, wherein the first p-type cladding layer has a thickness of 10 angstroms or more and 1.0 μm or less. Provided.
[0010]
The first n-type cladding layer preferably has a thickness of 10 angstroms or more and 1.0 μm or less, more preferably 100 angstroms or more and 1.0 μm or less.
[0011]
The first p-type cladding layer has a thickness of 10 angstroms or more and 1.0 μm or less, more preferably 100 angstroms or more and 0.5 μm or less.
[0013]
According to the second aspect of the present invention, an active layer having a quantum well structure including first and second main surfaces and including a nitride semiconductor containing indium and gallium, the first main of the active layer An n-type nitride semiconductor layer provided on a surface and a p-type nitride semiconductor layer provided on a second main surface of the active layer, the n-type nitride semiconductor layer comprising: A first n-type clad layer provided in contact with the first main surface of the active layer and made of n-type nitride semiconductor or n-type GaN containing indium and gallium; and the first n-type clad And a second n-type cladding layer made of a nitride semiconductor containing n-type GaN or aluminum and gallium, the p-type nitride semiconductor layer comprising: Provided in contact with the second main surface of the active layer, and aluminum And a first p-type cladding layer made of a p-type nitride semiconductor containing gallium and gallium, wherein the first p-type cladding layer has a thickness of 10 angstroms or more and 1.0 μm or less. A nitride semiconductor light emitting device is provided.
[0014]
In this nitride semiconductor light emitting device, a second p-type formed of p-type GaN or a p-type nitride semiconductor containing p-type GaN or indium and gallium is provided at a position farther from the active layer than the first p-type cladding layer. It is preferable to further include a cladding layer.
[0015]
The p-type nitride semiconductor layer preferably has a p-type contact layer on which a positive electrode is formed.
[0016]
In the nitride semiconductor light emitting device of the first and second side surfaces, it is preferable that the first n-type cladding layer is a nitride semiconductor containing indium and gallium.
[0017]
The n-type nitride semiconductor layer has an n-type contact layer on which a negative electrode is formed, and is formed of nitride semiconductors having different compositions between the n-type contact layer and the second n-type cladding layer. It is preferable to have an n-type multilayer light reflecting film. Similarly, the p-type nitride semiconductor layer has a p-type contact layer on which a positive electrode is formed, and nitride semiconductors having different compositions between the p-type contact layer and the second p-type cladding layer. It is preferable to have a p-type multilayer light reflecting film formed of
[0018]
In the multilayer light reflecting film, it is advantageous that at least one of the nitride semiconductors constituting the multilayer light reflecting film is a nitride semiconductor or GaN containing indium and gallium.
[0019]
The active layer has a single quantum well structure composed of a well layer having a thickness of 100 angstroms or less, a multiple layer formed by laminating a well layer made of a nitride semiconductor containing indium and gallium and a barrier layer made of a nitride semiconductor. A quantum well structure. The active layer is preferably non-doped.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, similar parts are often denoted by the same reference numerals.
[0021]
FIG. 1 is a schematic cross-sectional view showing the structure of a nitride semiconductor light emitting device according to one embodiment of the present invention.
[0022]
A nitride semiconductor light emitting device 10 shown in FIG. 1 has a semiconductor multilayer structure including an active layer 15 and a first n-type cladding layer 14 and a p-type cladding layer 16 sandwiching the active layer 15 on both sides. This semiconductor multilayer structure is provided on the substrate 11 via the buffer layer 12 and the n-type contact layer 13.
[0023]
The active layer 15 includes a nitride semiconductor containing indium and gallium. A nitride semiconductor containing indium and gallium is In_m Al_n Ga_1-mn N (where 0 <m <1, 0 ≦ n <1). Most preferably, the active layer 15 has the formula In_m Ga_1-m It includes a nitride semiconductor represented by N (where 0 <m <1). By changing the ratio of indium, that is, the value of m in each equation, the band gap can be changed so as to obtain light emission in the region from ultraviolet to red. In the following description, the formula In_m Ga_1-m A nitride semiconductor represented by N (where 0 <m <1) or an equivalent expression may be simply expressed as InGaN.
[0024]
The active layer 15 has a quantum well structure. By making the active layer 15 have a quantum well structure, a high-output light-emitting element can be realized by the strained quantum well effect, the exciton light-emitting effect, etc., whether it is an LED element or an LD element.
[0025]
In the present invention, the quantum well structure refers to a structure that causes light emission between quantum levels of a nitride semiconductor (InGaN) constituting an active layer, and is a concept including both a single quantum well structure and a multiple quantum well structure. is there.
[0026]
The single quantum well structure refers to a structure in which the well layer is composed of a single layer of nitride semiconductor having a single composition. That is, an active layer having a single quantum well structure is composed of only a single well layer, and two cladding layers sandwiching this active layer (ie, composed of, for example, a single composition InGaN) on both sides are barrier layers. Will be constructed.
[0027]
The multiple quantum well structure refers to a multilayer structure in which a well layer and a barrier layer are sequentially stacked. The minimum stacked structure of the multiple quantum well structure is a three-layer structure including one barrier layer and (two) well layers provided on both sides of the barrier layer, or one well layer and both sides thereof (2 Two) barrier layers. In the multiple quantum well structure, the two outermost layers on both sides are each constituted by a well layer or a barrier layer. In the case of a multiple quantum well structure in which the two outermost layers of the active layer are each composed of a well layer, two cladding layers sandwiching the active layer on both sides constitute a barrier layer. In the active layer of this multiple quantum well structure, the well layer and the barrier layer can both be formed of a nitride semiconductor containing indium and gallium (preferably InGaN) (however, the compositions of the two are different). The layer may be formed of a nitride semiconductor (preferably InGaN) containing indium and gallium, and the barrier layer may be formed of another nitride semiconductor, for example, InN or GaN. That is, the active layer of this multiple quantum well structure also includes a nitride semiconductor containing indium and gallium.
[0028]
In the case of a single quantum well structure, the active layer 15 is formed with a well layer having a thickness of 100 angstroms or less, and in the case of a multiple quantum well structure, each well layer is formed with a thickness of 100 angstroms or less and each barrier layer is 150 Å. It is preferable to form a thickness of angstrom or less. In any case, the well layer preferably has a thickness of 70 angstroms or less, and most preferably has a thickness of 50 angstroms or less. More preferably, the barrier layer in the active layer is formed to a thickness of 100 angstroms or less. The active layer having a multiple quantum well structure particularly preferably has a thickness of 200 angstroms or more, and can usually have a thickness of up to 0.5 μm.
[0029]
In either the single quantum well structure or the multiple quantum well structure, the active layer may be either n-type or p-type. Since exciton light emission or quantum well level light emission can be obtained, it is particularly preferable.
[0030]
When the active layer 15 is doped with a donor impurity and / or an acceptor impurity, if the crystallinity of the active layer doped with the impurity is substantially the same as the crystallinity of the non-doped active layer, the active layer doped with the donor impurity The interband emission intensity can be higher than that of the non-doped active layer, while the acceptor impurity-doped active layer emits light shifted to the lower energy side by about 0.5 eV from the peak wavelength of the original interband emission. Although the peak wavelength is shown, the half width tends to be widened. Further, when both the acceptor impurity and the donor impurity are doped, the emission intensity of the active layer doped with only the acceptor impurity can be further increased. In particular, when obtaining an active layer doped with an acceptor impurity, the conductivity type of the active layer is preferably doped with a donor impurity such as Si to be n-type.
[0031]
However, in the present invention, since it is ideal that the active layer emits light strongly by interband light emission, it is most preferable that the active layer 15 is not doped with impurities. In addition, a light emitting element having a non-doped active layer can have a lower Vf (forward voltage) than a light emitting element having an active layer doped with impurities.
[0032]
The first n-type cladding layer 14 provided in contact with the first main surface of the active layer 15 is formed of an n-type nitride semiconductor containing indium and gallium. The nitride semiconductor containing In and Ga acts as a buffer layer because the crystal is relatively soft, and other nitrides that can be formed on or on the active layer 15 and itself as described below. The semiconductor layer does not easily crack and does not deteriorate their crystallinity, thereby improving the light emission output of the light emitting element. The first n-type cladding layer 14 is preferably formed of n-type Inj Ga1-j N (0 <j <1). In Inj Ga1-j N, the value of j is preferably in the range of 0 <j ≦ 0.5. Generally, InGaN has a tendency that the crystallinity gradually deteriorates as the In ratio is increased. In order for the light-emitting element to emit light with practically high light output as an n-type cladding layer, the j value is 0. .5 or less is preferable. The j value is more preferably in the range of 0 <j ≦ 0.3, most preferably 0 <j ≦ 0.2.
[0033]
The carrier concentration of the first n-type cladding layer 14 is 1 × 10¹⁸/ Cm^Three ~ 1x10²⁰/ Cm^Three It is desirable to be within the range. The carrier concentration in the n-type cladding layer 14 is 1 × 10¹⁸/ Cm^Three If it is less, the efficiency of electron injection into the active layer 15 tends to decrease and the light emission output tends to decrease, while the carrier concentration in the n-type cladding layer 14 is 1 × 10 6.²⁰/ Cm^Three This is because the crystallinity of the first n-type cladding layer tends to deteriorate and the light emission output tends to decrease.
[0034]
The thickness of the first n-type cladding layer 14 is not particularly limited, but the active layer 15 and the first n-type cladding layer 14 preferably have a total thickness of 300 angstroms or more. If the total thickness of the nitride semiconductor layer containing In and Ga (active layer + first n-type cladding layer) is less than 300 angstroms, the active layer 15 and the first n-type cladding layer 14 are further This is because cracks are likely to occur in another nitride semiconductor layer provided in contact with one n-type cladding layer due to strain stress that may exist at the interface due to irregular lattice constant, difference in thermal expansion coefficient, or the like. As described above, a nitride semiconductor containing In and Ga is beneficial in relieving this stress because its crystal is relatively soft, but its total thickness is formed to a thickness of 300 angstroms or more. By doing so, the stress is further relaxed. This total thickness is preferably 1 μm or less.
[0035]
The p-type cladding layer 16 formed in contact with the second main surface of the active layer 15 is formed of a p-type nitride semiconductor. Such nitride semiconductors have the formula In_s Al_t Ga_1-st N (where 0 ≦ s, 0 ≦ t, s + t ≦ 1).
[0036]
The substrate 11 is made of sapphire (including C-plane, R-plane, and A-plane), SiC (including 6H-SiC, 4H-SiC), Si, ZnO, GaAs, spinel (MgAl₂ O_Four In particular, the (111) plane) can be formed of GaN, an oxide single crystal having a lattice constant close to that of a nitride semiconductor, and sapphire, spinel, GaN, or SiC is generally used.
[0037]
The buffer layer 12 formed on the substrate 11 is normally formed to alleviate lattice mismatch between the substrate 11 and the nitride semiconductor layer formed thereon. For example, GaN, AlN, GaAlN Etc. to form a thickness of several hundred angstroms. When the substrate 11 is formed of a material such as SiC or ZnO having a lattice constant close to that of the nitride semiconductor formed thereon, the substrate 11 is lattice-matched with the nitride semiconductor formed thereon. In this case, the buffer layer 12 may not be formed.
[0038]
On the buffer layer 12, an n-type contact layer 13 is formed in contact with the first n-type cladding layer 14. This n-type contact layer 13 is preferably formed of GaN, AlGaN or the like.
[0039]
After each predetermined semiconductor layer is formed on the substrate 11, a negative electrode 18 is formed on the surface of the n-type contact layer exposed by etching.
[0040]
When the n-type contact layer 13 is formed of GaN, a more preferable ohmic contact with the negative electrode 18 is achieved, and the forward voltage (V_f) Is further reduced. Also, since GaN is superior in crystallinity compared to other ternary mixed crystal and quaternary mixed crystal nitride semiconductors, nitride semiconductor layers such as the first n-type cladding layer 14 grown on the GaN mixed crystal are grown. Therefore, the light emission output of the light emitting element is improved.
[0041]
Also, the carrier concentration of the n-type contact layer 13 is such that the preferable ohmic contact with the negative electrode 18 is achieved and the resulting V_f5 × 10 from the viewpoint of the reduction of the light emission and the reduction of the light emission output¹⁷/ Cm^Three ~ 5x10¹⁹/ Cm^Three It is desirable to be within the range.
[0042]
From the viewpoint of achieving a preferable ohmic contact with the n-type contact layer 13, the negative electrode 18 is a metal material containing titanium (Ti) and gold (Au), for example, a laminated structure or alloy thereof, or Ti and aluminum (Al And the like, for example, a laminated structure or an alloy thereof. In this case, the negative electrode 18 is particularly preferably formed as a two-layer structure of a titanium layer provided in direct contact with the n-type GaN contact layer 13 and an aluminum layer formed thereon.
[0043]
A p-type contact layer 17 is formed on the p-type cladding layer 16, and a positive electrode 19 is formed thereon. The p-type contact layer 17 is preferably formed of GaN, AlGaN or the like. In particular, when the p-type contact layer 17 is formed of GaN, a more preferable ohmic contact with the positive electrode 19 is achieved, and the Vf of the light emitting element can be reduced.
[0044]
Achieving favorable ohmic contact with the positive electrode 19 and the resulting V_fFrom the standpoint of lowering the light emission and preventing the light emission output from decreasing, the carrier concentration of the p-type contact layer 17 is¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is desirable to be within the range.
[0045]
From the viewpoint of achieving a preferable ohmic contact with the p-type contact layer 17, the positive electrode 19 is most preferably formed of a metal material containing nickel (Ni) and gold (Au), for example, a laminated structure or an alloy thereof. . In this case, the positive electrode 19 is particularly preferably formed as a two-layer structure of a nickel layer provided in direct contact with the p-type GaN contact layer 17 and a gold layer formed thereon.
[0046]
FIG. 2 shows another embodiment of the nitride semiconductor light emitting device of the present invention.
[0047]
The light emitting element 20 shown in FIG. 2 has the nitride semiconductor element shown in FIG. 1 except that a second n-type cladding layer 21 is provided between the first n-type cladding layer 14 and the n-type contact layer 13. Has the same structure.
[0048]
In the light emitting element 20, the second n-type cladding layer 21 provided in addition to the light emitting element structure shown in FIG. 1 is formed of an n-type nitride semiconductor containing aluminum and gallium. By providing the second n-type cladding layer 21 as described above, the band gap difference from the first n-type cladding layer 14 can be increased, and the light emission efficiency of the light emitting element can be improved.
[0049]
This second n-type cladding layer 21 is preferably n-type Al._a Ga_1-a N (where 0 <a <1). In this case, the value of a is preferably in the range of 0 <a ≦ 0.6. AlGaN has a relatively hard crystal, and if it is larger than 0.6, cracks tend to occur relatively easily in the layer despite the presence of the first n-type cladding layer 14, and the light output tends to decrease. Because there is. The a value is most preferably in the range of 0 <a ≦ 0.4. In this specification, Al_a Ga_1-a A nitride semiconductor represented by N or an equivalent formula may be simply expressed as AlGaN.
[0050]
The carrier concentration of the second n-type cladding layer 21 is 5 × 10.¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is desirable to be within the range. Its carrier concentration is 5 × 10¹⁷/ Cm^Three Lower than that, the resistivity of AlGaN increases, so the V_f, And the luminous efficiency tends to decrease, while the carrier concentration is 1 × 10¹⁹/ Cm^Three This is because the crystallinity of AlGaN deteriorates and the luminous efficiency decreases. The second n-type cladding layer 21 can usually be formed with a thickness of 50 Å to 0.5 μm.
[0051]
The substrate 11, the buffer layer 12, the n-type contact layer 13, the n-type cladding layer 14, the active layer 15, the p-type cladding layer 16, the p-type contact layer 17, the negative electrode 18 and the positive electrode 19 are as described with reference to FIG. belongs to.
[0052]
FIG. 3 is a schematic cross-sectional view showing another structure of the nitride semiconductor light emitting device according to the present invention.
[0053]
The nitride semiconductor light emitting device 30 shown in FIG. 3 has a semiconductor multilayer structure including an active layer 15 and an n-type cladding layer 34 and a first p-type cladding layer 36 sandwiching the active layer 15 on both sides. This semiconductor stacked structure is provided on the substrate 11 via the buffer layer 12 and the n-type contact layer 13 as in the structure shown in FIG.
[0054]
The first p-type cladding layer 36 provided in contact with the second main surface of the active layer 15 is formed of a p-type nitride semiconductor containing indium and gallium. The nitride semiconductor containing In and Ga has a relatively soft crystal, so that it acts as a buffer layer, and other nitride semiconductors that can be formed on or on the active layer 15 and itself as described below. The layer does not easily crack and does not deteriorate their crystallinity, thereby improving the light emission output of the light emitting element. The first p-type cladding layer 36 is made of p-type In_k Ga_1-k It is desirable to form with N (0 <k <1). This In_k Ga_1-k In N, the value of k is preferably in the range of 0 <k ≦ 0.5. InGaN generally has a tendency that the crystallinity gradually deteriorates as the In ratio is increased. In order to cause the light-emitting element to emit light with practically high light output as a p-type cladding layer, the k value is 0. .5 or less is preferable. The k value is more preferably in the range of 0 <k ≦ 0.3, most preferably 0 <k ≦ 0.2.
[0055]
The carrier concentration of the first p-type cladding layer 36 is 1 × 10¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is desirable to be within the range. The carrier concentration in the first p-type cladding layer 36 is 1 × 10¹⁷/ Cm^Three If it is less, the efficiency of electron injection into the active layer 15 tends to decrease and the light emission output tends to decrease, while the carrier concentration in the p-type cladding layer 36 is 1 × 10.¹⁹/ Cm^Three This is because the crystallinity of the first p-type cladding layer deteriorates and the light emission output tends to decrease. The first p-type cladding layer 36 is preferably obtained by the method described for the p-type cladding layer 16 in the structure shown in FIG.
[0056]
The thickness of the first p-type cladding layer 36 is not particularly limited, but the active layer 15 and the first p-type cladding layer 36 desirably have a total thickness of 300 angstroms or more. If the total thickness of the nitride semiconductor layer containing In and Ga (active layer + first p-type cladding layer) is less than 300 angstroms, the active layer 15 and the first p-type cladding layer 36 will be further This is because cracks are likely to occur in another nitride semiconductor layer provided in contact with one p-type clad layer due to strain stress that may exist at the interface due to irregular lattice constant, difference in thermal expansion coefficient, or the like. As described above, a nitride semiconductor containing In and Ga is beneficial in relieving this stress because its crystal is relatively soft, but its total thickness is formed to a thickness of 300 angstroms or more. By doing so, the stress is further relaxed. This total thickness is preferably 1 μm or less.
[0057]
The n-type cladding layer 34 formed in contact with the first main surface of the active layer 15 is formed of an n-type nitride semiconductor. Such nitride semiconductors have the formula In_u Al_v Ga_1-uv N (where 0 ≦ u, 0 ≦ v, u + v ≦ 1).
[0058]
The substrate 11, the buffer layer 12, the n-type contact layer 13, the active layer 15, the p-type contact layer 17, the negative electrode 18, and the positive electrode 19 are as described with reference to FIG.
[0059]
FIG. 4 shows another embodiment of the nitride semiconductor light emitting device according to the present invention.
[0060]
4 is the nitride semiconductor device shown in FIG. 3 except that the second p-type cladding layer 41 is provided between the first p-type cladding layer 36 and the p-type contact layer 17. Has the same structure.
[0061]
In the light emitting element 40, the second p-type cladding layer 41 provided in addition to the light emitting element structure shown in FIG. 3 is formed of a p-type nitride semiconductor containing aluminum and gallium. By providing such a second p-type cladding layer 41, the band gap difference with the first p-type cladding layer 36 can be increased, and the light emission efficiency of the light emitting element can be improved.
[0062]
The second p-type cladding layer 41 is preferably p-type Al._b Ga_1-b N (where 0 <b <1). In this case, the value of b is preferably in the range of 0 <b ≦ 0.6. AlGaN has a relatively hard crystal, and if it is larger than 0.6, cracks are relatively likely to occur in the layer despite the presence of the first p-type cladding layer 36, and the light output tends to decrease. Because there is. The b value is most preferably in the range of 0 <b ≦ 0.4.
[0063]
The carrier concentration of the second p-type cladding layer 41 is 1 × 10¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is desirable to be within the range. Its carrier concentration is 1 × 10¹⁷/ Cm^Three Lower than that, the efficiency of hole injection into the active layer 15 tends to decrease and the light emission efficiency tends to decrease, while the carrier concentration is 1 × 10 6.¹⁹/ Cm^Three This is because the crystallinity of AlGaN deteriorates and the luminous efficiency decreases. The second p-type cladding layer 41 can usually be formed with a thickness of 50 Å to 0.5 μm.
[0064]
The substrate 11, the buffer layer 12, the n-type contact layer 13, the active layer 15, the p-type contact layer 17, the negative electrode 18 and the positive electrode 19 are as described with reference to FIG. One p-type cladding layer 36 is as described with reference to FIG.
[0065]
FIG. 5 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
[0066]
The nitride semiconductor light emitting device 50 shown in FIG. 5 includes an active layer 15, an n-type semiconductor layer 501 including a first n-type cladding layer 54 sandwiching the active layer 15 on both sides, and a second p-type cladding layer 41. It has a semiconductor stacked structure including the p-type semiconductor layer 502 included. This semiconductor stacked structure is provided on the substrate 11 via the buffer layer 12 and the n-type contact layer 13 as in the structure shown in FIG. In FIG. 5, the n-type semiconductor layer 501 is composed of a first n-type cladding layer 54.
[0067]
This light-emitting element 50 can be said to have a semiconductor laminated structure in which the n-type cladding layer structure in the light-emitting element 10 shown in FIG. 1 and the p-type cladding layer structure shown in FIG. 4 are combined. The first n-type cladding layer 54 can be formed not only by the nitride semiconductor containing indium and gallium constituting the first n-type cladding layer 14 shown in FIG. 1, but also by GaN, and has the same effect. I understood. In this case, the first p-type cladding layer 56 may be formed of any p-type nitride semiconductor, similar to the p-type cladding layer 16 in the light emitting device 10 shown in FIG. . Even with such a semiconductor laminated structure, the light emitting element exhibits the same excellent characteristics.
[0068]
More specifically, the first n-type cladding layer 54 is formed of an n-type nitride semiconductor that does not contain aluminum. The first n-type cladding layer 54 is made of n-type In_w Ga_1-w N (where 0 ≦ w <1) is preferable. That is, the first n-type cladding layer 54 can be formed of the n-type nitride semiconductor described with respect to the first n-type cladding layer 14 in the light emitting device 10 shown in FIG. can do. For the same reason as described for the first n-type cladding layer 14 in the light emitting device 10 shown in FIG. 1, the value of w is preferably in the range of 0 ≦ w ≦ 0.5, more preferably It is in the range of 0 <w ≦ 0.3, most preferably 0 <w ≦ 0.2. For the same reason, the carrier concentration of the first n-type cladding layer 54 is 1 × 10 6.¹⁸/ Cm^Three ~ 1x10²⁰/ Cm^Three It is desirable to be within the range. The thickness of the first n-type cladding layer 54 is not particularly limited, but for the same reason, the active layer 15 and the first n-type cladding layer 54 have a total thickness of 300 angstroms or more. Desirably, it may have a thickness of 1 μm or less.
[0069]
In the light emitting device 50 shown in FIG. 5, the first p-type cladding layer 56 formed in contact with the second main surface of the active layer may be formed of any p-type nitride semiconductor, but aluminum It is preferable to form a p-type nitride semiconductor that does not contain any of these. More specifically, the first p-type cladding layer 56 is preferably formed of p-type Inx Ga1-x N (where 0 ≦ x <1). For the same reason as described for the first p-type cladding layer 36 in the light emitting element 30 of FIG. 3, the x value is preferably in the range of 0 ≦ x ≦ 0.5, more preferably 0 ≦. It is in the range of x ≦ 0.3, most preferably in the range of 0 ≦ x ≦ 0.2. The first p-type clad layer 56 is also formed of GaN in the same manner, and functions similarly as a buffer layer. The carrier concentration of the first p-type cladding layer 56 is also 1 × 10 6 for the same reason.¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is desirable to be within the range. Further, the thickness of the first cladding layer 56 is not particularly limited, but for the same reason, it is desirable that the total thickness with the active layer 15 is 300 angstroms or more, and a thickness of 1 μm or less is preferable. . The first p-type cladding layer 56 may be omitted. However, if the first p-type cladding layer 56 is formed, the first p-type cladding layer acts as a buffer layer, so that cracks are less likely to occur. It will be clear that it exhibits even better properties.
[0070]
The second p-type cladding layer 41 is as described for the second cladding layer 41 in the light emitting device 40 shown in FIG.
[0071]
The substrate 11, the buffer layer 12, the n-type contact layer 13, the p-type contact layer 17, the negative electrode 18, and the positive electrode 19 are as described for the light-emitting element 10 shown in FIG.
[0072]
FIG. 6 is a schematic sectional view showing the structure of still another embodiment of the semiconductor light emitting device according to the present invention. The light emitting device 60 is the same as the light emitting device 50 shown in FIG. 5 except that the second n-type cladding layer 21 is additionally formed between the n-type contact layer 13 and the first n-type cladding layer 54. It has a similar structure. The second n-type cladding layer 21 is as described for the second n-type cladding layer 21 in the light emitting device 20 shown in FIG. The first p-type cladding layer 56 is preferably provided rather than omitted, as in the case of the light emitting element 50 shown in FIG.
[0073]
Although several nitride semiconductor light emitting devices according to the present invention have been described above, it goes without saying that the structure of these light emitting devices can be applied to both LED devices and LD devices. For example, the LD has a structure shown in a perspective view in FIG. In FIG. 7, a semiconductor layer 71 on the substrate 11 is a semiconductor layer comprising the buffer layer 12, the n-type contact layer 13, the first n-type cladding layer, and the second n-type layer when formed. The semiconductor layer 72 formed on the active layer 15 is a semiconductor layer including the first clad layer, the second clad layer, and the p-type contact 17 layer formed as described above. The applied current flows concentratedly in the region 15 a corresponding to the positive electrode 19 in the active layer 15.
[0074]
In the case of an LD element, a second n-type cladding layer is formed between the first n-type cladding layer of any one of the light emitting elements 10 to 60 and the n-type contact layer 13. Is between the second n-type cladding layer and the n-type contact layer 13 and / or between the first p-type cladding layer of any one of the light emitting elements 10 to 60 and the p-type contact layer 17. When the second p-type cladding layer is formed, at least two types of nitride semiconductor layers having different compositions are laminated between the second p-type cladding layer and the n-type contact layer 13. The multilayer film thus formed can be formed as a light reflecting film.
[0075]
An example in which the multilayer light reflecting film is applied to the light emitting element structure shown in FIG. 6 is shown in FIG. A nitride semiconductor light emitting device 80 shown in FIG. 8 includes a first multilayer light reflecting film (n-type) 81 between the n-type contact layer 13 and the second n-type cladding layer 21, and a second p-type. A second multilayer light reflecting film (p-type) 82 is provided between the cladding layer 41 and the p-type contact layer 17.
[0076]
Each of the first multilayer film 81 and the second multilayer film 82 is made of nitride semiconductors having different compositions, that is, nitride semiconductors having different refractive indexes, and each layer is, for example, λ / 4n (where λ is active It is formed by alternately laminating two or more layers with a thickness calculated by the wavelength of the emitted light from the layer 15, where n is the refractive index, so that the emitted light from the active layer 15 can be reflected by these films. Designed to. When the positive electrode 19 is formed as a stripe electrode having a shape as shown in FIG. 7, for example, with a width of 10 μm or less and laser oscillation is performed, the light emitted from the active layer 15 can be confined in the active layer 15 by the multilayer reflective layer. Since it can be much easier, laser oscillation can be easily performed. Also in the LED mode, leakage of emitted light is suppressed by the multilayer reflective layer, and the external quantum efficiency is improved.
[0077]
Each of the multilayer light reflecting films 81 and 82 is doped with a donor impurity and an acceptor impurity to have a predetermined conductivity type.
[0078]
In the structure shown in FIG. 8, the first multi-light reflecting layer film 81 is formed between the n-type contact layer 13 and the second n-type cladding layer 21, but instead of this, Can also be formed in the n-type contact layer 13. Similarly, the second multilayer light reflecting film 82 may be formed in the p-type contact layer 17. Even if the multilayer light reflecting film is formed in the contact layer, the light emitted from the active layer 16 can be confined in the same manner. Further, either the first multilayer light reflecting film 81 or the second multilayer light reflecting film 82 may be omitted.
[0079]
As shown in FIG. 8, when a laser element is manufactured using an insulating material such as sapphire as a substrate 11, the structure of the laser element is a flip chip method. That is, the positive and negative electrodes 19 and 18 are formed on the same surface side of the substrate 11, more specifically, on the nitride semiconductor layer forming side of the substrate 11. In this case, as shown in FIG. 8, the first multilayer light reflecting film 81 formed on the n-type layer side is on the p-layer side, that is, above the horizontal surface of the n-type contact layer 13 on which the negative electrode 18 is formed. It is preferable to form in a position. When the first multilayer light reflecting film 81 is formed closer to the substrate 11 than the horizontal surface of the n-type contact layer 13, the difference in refractive index between the second n-type cladding layer 21 and the n-type contact layer 13 is small. This is because light emitted from the active layer 15 spreads into the n-type contact layer 13 located below the active layer 15 and sufficient light confinement may not be achieved. This is a phenomenon peculiar to a nitride semiconductor laser using an insulating substrate such as sapphire.
[0080]
At least one of the two types of nitride semiconductors constituting each of the multilayer light reflecting films 81 and 82 is a nitride semiconductor containing at least one of indium and gallium (for example, In_q Ga_1-qN (where 0 <q <1)) or GaN is preferable. This is because when a single layer is laminated to form a multilayer light reflecting film, one of the single layers is formed of InGaN or GaN so that the InGaN or GaN layer acts like a buffer layer and the other single layer is formed. This is because it is possible to prevent cracks from forming further. This is because the crystals of the InGaN layer and the GaN layer are softer than AlGaN. On the other hand, if the multilayer light reflecting film is formed by using AlGaN layers having different Al compositions, for example, so as to have a total film thickness of 0.5 μm or more, cracks are formed in the multilayer film, making it difficult to manufacture the device.
[0081]
The best combination of the two types of nitride semiconductor layers constituting each multilayer light reflecting film is that one of them is In as described above._c Ga_1-c Nitride semiconductor formed of N or GaN and the other containing aluminum and / or gallium (for example, Al_c Ga_1-c N (where 0 ≦ c <1)). In_q Ga_1-q N and Al_c Ga_1-c Since the difference in refractive index from N is large, it is possible to design a multilayer light reflecting film having a high reflectance according to the emission wavelength by forming the multilayer light reflecting film with these materials. Also, In_q Ga_1-q Since N can act as a buffer layer, Al_c Ga_1-c Ten or more layers can be laminated without cracks in the N layer. The refractive indices of InN, GaN, and AlN are 2.9, 2.5, and 2.15, respectively. The refractive index of these mixed crystals is assumed to follow Vegard's law and can be determined as being proportional to the composition.
[0082]
FIG. 9 is a schematic sectional view showing the structure of still another embodiment of the nitride semiconductor light emitting device according to the present invention, and shows the structure as an LD device.
[0083]
A nitride semiconductor light emitting device 90 shown in FIG. 9 has a semiconductor stacked structure including an active layer 95 and an n-type nitride semiconductor layer 94 and a p-type nitride semiconductor layer 96 sandwiching the active layer 95 on both sides. This semiconductor multilayer structure is provided on the substrate 91 via the buffer layer 92 and the n-type contact layer 93.
[0084]
The active layer 95 has a quantum well structure (single quantum well structure or multiple quantum well structure) including a nitride semiconductor containing indium and gallium, like the active layer 15 in the semiconductor light emitting device 10 shown in FIG. The above description of the active layer 15 is also applied to the active layer 95 as it is.
[0085]
The p-type nitride semiconductor layer 96 includes a first p-type cladding layer 96a formed in direct contact with the second main surface of the active layer 95 and a second p-type cladding layer 96a formed on the first p-type cladding layer 96a. P-type cladding layer 96b.
[0086]
The first p-type cladding layer 96a is formed of a p-type nitride semiconductor containing aluminum and gallium. When the first p-type cladding layer 96a is formed of a nitride semiconductor containing aluminum and gallium, the optical confinement in the active layer 95, which may be insufficient due to the quantum well structure, becomes more complete. It has been found that the p-type cladding layer 95 acts as a good light guide layer for confining light in the active layer 95.
[0087]
The first p-type cladding layer 96a is most preferably formed of p-type Ald Ga1-d N (where 0 <d <1). This is because AlGaN can be easily obtained as a p-type having a high carrier concentration, and the band gap difference and the refractive index difference can be made larger than those of other nitride semiconductors with respect to the active layer 95 containing InGaN. In addition, p-type AlGaN has a property that it is difficult to decompose during growth as compared with other nitride semiconductors. For example, when this is grown by metal organic vapor phase epitaxy (MOVPE), As a result, the active layer 95 having excellent crystallinity is provided, and the output of the light emitting element is improved.
[0088]
The first p-type cladding layer 96a preferably has a thickness of 10 Å or more and 1.0 μm or less. If the thickness is less than 10 angstroms, the effect of providing the first p-type cladding layer cannot be obtained. On the other hand, if the thickness is more than 1.0 μm, the first p-type cladding layer itself is cracked. Since it becomes easy to enter, the device creation tends to be difficult. More preferably, the first p-type cladding layer 96a has a thickness of 10 Å or more and 0.5 μm or less.
[0089]
In general, the first p-type cladding layer 96a preferably has a thickness within the above range including the case of an LED element, but particularly in the case of an LD element, it is 100 angstroms or more (for the same reason). , 1.0 μm or less) is more preferable. If the thickness is less than 100 angstroms, the first p-type cladding layer is less likely to act as a light guide layer. In this case, the first p-type cladding layer 96a most preferably has a thickness of not less than 100 angstroms and not more than 0.5 μm.
[0090]
The second p-type cladding layer 96b provided on the first p-type cladding layer 96a has a larger band gap than the first p-type cladding layer 96a, and is formed of a p-type nitride semiconductor containing aluminum and gallium. The It can be seen that by forming the second p-type cladding layer 96b from such a p-type nitride semiconductor, the second cladding layer effectively acts as an optical confinement layer and can provide an effective LD element or the like. It was.
[0091]
As in the case of the first p-type cladding layer 96a, the second p-type cladding layer 96b can be easily obtained as a p-type layer having a high carrier concentration._eGa_1-e Most preferably, N is formed (where 0 <e <1). In addition, when the second p-type cladding layer 96b is formed of p-type AlGaN, the band gap difference and the refractive index difference from the first p-type cladding layer can be increased. It becomes more effective as a layer. Since the second p-type cladding layer 96b has a larger band gap than the first p-type cladding layer 96a, for example, Al constituting the former is used._e Ga_1-e The value of f in N is the Al constituting the latter._d Ga_1-d It takes a value larger than the value of e in N. Even in this case, if possible, it is desirable that the d value and the e value in these expressions are more than 0 and 0.6, and more preferably more than 0 and 0.4.
[0092]
The thickness of the second p-type cladding layer 96b is not particularly limited, but preferably has a thickness of about 500 angstroms to 1 μm. By forming the second p-type cladding layer to such a thickness, a p-type AlGaN layer having fewer cracks in itself and hence better crystallinity and having a high carrier concentration can be obtained. is there.
[0093]
The first p-type cladding layer 96a and the second p-type cladding layer 96b are both 1 × 10¹⁷~ 1x10¹⁹/ Cm^Three Can be provided as having a high carrier concentration.
[0094]
Further, a layer made of p-type InGaN or p-type GaN may be formed between the first p-type cladding layer 96a and the second p-type cladding layer 96b to a thickness of 10 angstroms to 1 μm. This layer acts as a light guide layer and a buffer layer.
[0095]
The n-type cladding layer 94 provided in contact with the first main surface of the active layer 95 can be formed of any n-type nitride semiconductor. However, since the n-type cladding layer 94 can be formed as a layer having further excellent crystallinity, it is preferable to form the n-type mixed crystal or ternary mixed crystal nitride semiconductor such as GaN, AlGaN, or InGaN. . In particular, by forming the n-type cladding layer 94 from InGaN or GaN, a better active layer 95 can be provided on the n-type cladding layer 94, and the output of the light emitting device is remarkably improved.
[0096]
In the case of an LD element, the n-type cladding layer 94 is desirably formed with a film thickness of 100 Å or more and 1 μm or less.
[0097]
The substrate 91 is the same as the substrate 11 in the light emitting element 10 shown in FIG. 1, and the above description of the substrate 11 can be applied to the substrate 91 as it is.
[0098]
The buffer layer 92 formed over the substrate 92 is also the same as the buffer layer 12 in the light emitting element 10 shown in FIG. 1, and the above description of the buffer layer 12 can be applied to the buffer layer 12 as it is. Similarly, in a special case, the buffer layer 92 can be omitted.
[0099]
The n-type contact layer 93 provided on the buffer layer 92 is also the same as the n-type contact layer 13 in the light emitting element 10 shown in FIG. 1, and the above description of the n-type contact layer 13 is the n-type contact. The same applies to the layer 93 as it is.
[0100]
The p-type contact layer 97 provided on the second p-type cladding layer 96b is also the same as the p-type contact layer 17 in the light emitting device shown in FIG. This p-type contact layer 97 can be applied as it is.
[0101]
The negative electrode 98 formed on the exposed surface of the n-type contact layer 93 is also the same as the negative electrode 18 in the light emitting element shown in FIG. 1, and the above description of the negative electrode 18 also applies to the negative electrode 98 as it is. Applicable.
[0102]
The positive electrode 99 provided in connection with the p-type contact layer 97 is also the same as the positive electrode 19 in the light emitting element shown in FIG. 1, and the above description of the positive electrode 19 is applied to the positive electrode 99 as it is. Applicable. However, in the LD structure shown in FIG. 9, on the p-type contact layer 97, a current confinement layer 100 having a through hole 100a and formed of an insulating material such as silicon dioxide is provided. The p-type contact layer 97 is in contact with the current confinement layer 100 through the through hole 100a.
[0103]
Although the present invention has been described mainly with reference to FIG. 9 with respect to the LD element, it is not necessary to provide the current confinement layer 100 in the case of an LED element. In the case of an LED element, the second p-type cladding layer 96b can be omitted. Further, in the case of an LED element, the preferred thickness of the n-type cladding layer 94 is 10 angstroms or more and 1.0 μm or less, more preferably 30 angstroms to 1.0 μm, or the n-type cladding layer 94 itself is omitted. You can also. When the n-type cladding layer 94 is omitted, the n-type contact layer 93 can act as a cladding layer. In the case of the LED element, in the structure shown in FIG. 9, the n-type cladding layer 94 is omitted, the second p-type cladding layer 96b is omitted, and the current confinement layer 100 is also omitted. A p-type contact layer 97 formed of p-type GaN, that is, an active layer having a quantum well structure including a nitride semiconductor containing indium and gallium, on the first main surface thereof The p-type nitride semiconductor layer containing aluminum and gallium is formed on the second main surface of the active layer, and the p-type GaN layer is formed on the p-type nitride semiconductor. What has a structure is the most preferable LED element structure. This corresponds to the nitride semiconductor light emitting device according to one aspect of the present invention.
[0104]
FIG. 10 is a schematic cross-sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention, and shows the structure as an LD device as in FIG.
[0105]
A nitride semiconductor light emitting device 200 shown in FIG. 10 has a semiconductor multilayer structure including an active layer 95 and an n-type nitride semiconductor layer 294 and a p-type nitride semiconductor layer 296 sandwiching the active layer 95 on both sides. This semiconductor multilayer structure is provided on the substrate 91 via the buffer layer 92 and the n-type contact layer 93.
[0106]
The n-type nitride semiconductor layer 294 includes a first n-type cladding layer 294a formed in direct contact with the first main surface of the active layer 95 and a second n-type cladding layer 294a formed on the first n-type cladding layer 294a. N-type cladding layer 294b.
[0107]
The first n-type cladding layer 294a is formed of n-type GaN or an n-type nitride semiconductor containing indium and gallium. When the first n-type cladding layer 294a is formed of GaN or a nitride semiconductor containing indium and gallium, the optical confinement in the active layer 95, which may be insufficient due to the quantum well structure, becomes more complete. The first n-type cladding layer 294a not only functions as a good light guide layer for confining light in the active layer 95 (in the case of an LD element), but also the first n-type cladding layer serves as a buffer layer. It has been found that it is possible to reduce the generation of cracks in the active layer 95 formed on the active layer 95 and to increase the light emission output of the light emitting element.
[0108]
The first n-type cladding layer 294a is made of In_r Ga_1-r Most preferably, N is formed (where 0 <r <1). In this case, for the same reason as described above, the value of r is preferably up to 0.5, more preferably up to 0.3, and even more preferably up to 0.2. Also, the carrier concentration is 1 × 10 for the same reason as above.¹⁸/ Cm^Three ~ 1x10²⁰/ Cm^Three It is preferable that
[0109]
The first n-type cladding layer 294a preferably has a thickness of 10 angstroms or more. By forming the first n-type cladding layer 294a to a thickness of 10 angstroms or more, the first n-type cladding layer 294a functions more effectively as a buffer layer between the active layer 95 and the second n-type cladding layer 294b described below. . That is, since the crystal of InGaN or GaN constituting the first n-type cladding layer 294a is relatively soft, the lattice constant mismatch and the thermal expansion coefficient between the second n-type cladding layer 294b and the active layer 23 The strain caused by the difference can be absorbed more effectively, and the buffer layer can function more effectively. As a result, even if the active layer 95 is sufficiently thin, the presence of the first n-type cladding layer 294a causes cracks in the active layer 95, the second n-type cladding layer 294b, and hence the p-type cladding layer 296. Is difficult to enter, and the crystallinity thereof becomes good, so that the light emission output of the light emitting element is further increased.
[0110]
The first n-type cladding layer 294a preferably has a thickness within the above range in the case of an LED element, but particularly preferably has a thickness of 100 angstroms or more in the case of an LD element. When the thickness is less than 100 angstroms, it becomes difficult to act as a light guide layer.
[0111]
In any case, the first n-type cladding layer 294a preferably has a thickness of 1.0 μm or less. If the thickness is greater than 1.0 μm, the crystal color tends to be dark and a large number of pits tend to be generated in the crystal. Therefore, it is difficult to obtain high-power LEDs and LD elements. Can be.
[0112]
The second n-type cladding layer 294b provided in contact with the first n-type cladding layer 294a may be formed of any nitride semiconductor as long as the band gap is larger than that of the first n-type cladding layer 294a. For example, it can be formed of a binary semiconductor or ternary nitride semiconductor such as GaN or AlGaN. By forming the second n-type cladding layer 294b from such an n-type nitride semiconductor, the second n-type cladding layer 294b effectively acts as an optical confinement layer, and provides an effective LD element and the like. I knew it was possible.
[0113]
The second n-type cladding layer 294b is most preferably formed of n-type Alf Ga1-fN (where 0 <f <1). This is because n-type AlGaN can increase the band gap difference and the refractive index difference with respect to the active layer 95 containing InGaN as compared with other nitride semiconductors. In this case, the value of f is preferably up to 0.6 and more preferably up to 0.4 for the same reason as described above. The carrier concentration is 5 × 10 5 for the same reason as above.¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is preferable that In addition, by providing a layer made of n-type InGaN between the second n-type clad layer 294b and the n-type contact layer 93, the second n-type clad layer made of AlGaN can generate cracks with good crystallinity. You can grow with less.
[0114]
The thickness of the second n-type cladding layer 294b is not particularly limited, but preferably has a thickness of 500 Å or more and 1.0 μm or less. By forming the second n-type cladding layer 294b with a thickness within this range, the second n-type cladding layer 294b having excellent crystallinity without cracks can be obtained.
[0115]
The p-type semiconductor layer (cladding layer) 296 provided in contact with the second main surface of the active layer 95 can be formed of any p-type nitride semiconductor. However, the p-type cladding layer 296 is preferably formed of p-type AlGaN because it can be formed as a layer with even better crystallinity. The p-type AlGaN has a property that it is difficult to be decomposed during growth as compared with other nitride semiconductors. For example, when the p-type AlGaN is grown by metal organic vapor phase epitaxy (MOVPE), the lower active layer The decomposition of 95 InGaN is suppressed, and as a result, the active layer 95 having excellent crystallinity is provided, thereby improving the output of the light emitting element. In this case, it is also preferable that the aluminum ratio and the carrier concentration take values that are preferable for the first p-type cladding layer 96a and the second p-type cladding layer 96b in the light-emitting element 90 shown in FIG. .
[0116]
In the case of an LD element, the p-type cladding layer 296 is desirably formed with a film thickness of 100 Å or more and 1 μm or less.
[0117]
Active layer 95, substrate 91, buffer layer 92 formed on substrate 91, n-type contact layer 93 provided on buffer layer 92, p-type contact layer 97, negative electrode 98, positive electrode 99 and The current confinement layer 100 is as described for the light emitting element shown in FIG.
[0118]
Now, the present invention has been described mainly with reference to FIG. 10 for LD elements, but in the case of LED elements, it is not necessary to provide the current confinement layer 100. In the case of an LED element, the second n-type cladding layer 294b can be omitted. In that case, the n-type contact layer 93 functions as a second n-type cladding layer.
[0119]
FIG. 11 is a schematic cross-sectional view showing the structure of still another embodiment of the nitride semiconductor light emitting device according to the present invention, and shows the structure as an LD device, similar to FIGS.
[0120]
A nitride semiconductor light emitting device 300 shown in FIG. 11 has a semiconductor multilayer structure including an active layer 95 and an n-type nitride semiconductor layer 294 and a p-type nitride semiconductor layer 96 sandwiching the active layer 95 on both sides. This semiconductor multilayer structure is provided on the substrate 91 via the buffer layer 92 and the n-type contact layer 93.
[0121]
The light-emitting element 300 shown in FIG. 11 has an n-type nitride semiconductor layer 294 (first n-type cladding layer 294a and second n-type cladding layer 294b in the light-emitting element 200 shown in FIG. For the p-type nitride semiconductor layer, the p-type nitride semiconductor layer 96 (consisting of the first p-type cladding layer 96a and the second p-type cladding layer 96b) in the light emitting device 90 shown in FIG. 9 is used. It is applied and is one of the most preferred embodiments of the present invention. 9 and 10 including the above description of the nitride semiconductor layer that can be omitted particularly in the case of an LED element and the thickness of the nitride semiconductor layer particularly in the case of an LED element. The explanations can be applied as they are and no other words are required. Therefore, in the light emitting device shown in FIG. 11, the n-type contact layer 93 is made of n-type GaN, the second n-type cladding layer 294b is made of n-type AlGaN, and the first n-type cladding layer 294a is made of n-type InGaN or n-type. The first p-type cladding layer 96a is made of p-type AlGaN, the second p-type cladding layer 96b is made of p-type AlGaN, the p-type contact layer 97 is made of p-type GaN, and the active layer 95 is non-doped. Is most preferable. In the case of the LD element structure shown in FIG. 11, it goes without saying that the first n-type cladding layer 294a is the optical guide layer, the second cladding layer 294b is the optical confinement layer, and the first p-type cladding layer. It is also clear that 96a acts as a light guide layer and the second p-type cladding layer 96b acts as a light confinement layer. Further, a layer made of p-type InGaN or p-type GaN may be formed as a buffer layer between the first p-type cladding layer 96a and the second p-type cladding layer 96b. A layer made of n-type InGaN may be formed as a buffer layer between the second n-type cladding layer 294b.
[0122]
According to one aspect of the present invention, an active layer having a quantum well structure including a nitride semiconductor containing indium and gallium is provided between an n-type nitride semiconductor layer and a p-type nitride semiconductor layer, and p The type nitride semiconductor layer includes a first p-type cladding layer made of a p-type nitride semiconductor formed in contact with the active layer and containing aluminum and gallium, and the first p-type cladding layer is 10 angstroms or more, A nitride semiconductor light emitting device having a thickness of 1.0 μm or less is provided.
[0123]
The light emitting device according to this aspect basically corresponds to a special case in which the second p-type cladding layer 96b is omitted from the structure of the light emitting device 90 shown in FIG. In this special case, either the n-type contact layer 93 or the n-type cladding layer 94 may be omitted from the structure of the light emitting device shown in FIG. 9 (the n-type cladding layer 94 is omitted). In this case, the n-type contact layer 93 functions as an n-type cladding layer), and the p-type contact layer 97 may also be omitted.
[0124]
Furthermore, in this special case, the second p-type clad layer corresponding to the second p-type clad layer 96b in the light emitting device 90 shown in FIG. 9 is made of p-type GaN or p-type nitride containing indium and gallium. A material semiconductor (preferably InGaN) can be used, and the description of the n-type cladding layer 14 in the light-emitting element 10 shown in FIG. 1 can be applied to this. Furthermore, in contact with the n-type cladding layer (first n-type semiconductor layer) corresponding to the n-type cladding layer 94 in the light emitting device 90 shown in FIG. 9, that is, the first n-type cladding layer 94 and the n-type contact layer. It is also preferable to provide a second n-type nitride semiconductor (preferably AlGaN) containing n-type GaN or aluminum and gallium. In this case, the description of the second n-type cladding layer 21 in the light-emitting element 20 shown in FIG. 2 including the n-type GaN layer can be applied.
[0125]
FIG. 12 is a schematic cross-sectional view showing the structure of still another embodiment of the nitride semiconductor light emitting device according to the present invention, and shows one particularly preferable structure as an LD device. The nitride semiconductor light emitting device of FIG. 12 can be said to substantially correspond to the preferred embodiment of the present invention described with reference to FIG. 6 except for the first p-type cladding layer described below.
[0126]
A nitride semiconductor light emitting device 400 shown in FIG. 12 includes an active layer 405, and a first n-type cladding layer 414, a second n-type cladding layer 424, and an n-type contact layer are formed on a first main surface thereof. An n-type semiconductor layer including 403 is provided. In addition, on the second main surface of the active layer 405, the first p-type cladding layer 416, the second p-type cladding layer 426, the third p-type cladding layer 436, and the p-type contact as the outermost layer are provided. A p-type nitride semiconductor layer including the layer 407 is included. In the structure shown in FIG. 12, such a stacked structure is provided over the substrate 401 with the buffer layer 402 interposed therebetween.
[0127]
The active layer 405 includes a nitride semiconductor containing indium and gallium, and constitutes a structure that causes light emission between quantum levels of the nitride semiconductor containing indium and gallium, in other words, a quantum well structure. . With respect to such a structure, all the explanations regarding the active layer 15 of the light emitting element 10 shown in FIG. In the case of an LD element, the active layer 405 most preferably has a multiple quantum well structure.
[0128]
The first n-type cladding layer 414 provided in contact with the first main surface of the active layer 405 functions as an optical guide layer, and is made of an n-type nitride semiconductor or n-type GaN containing indium and gallium. Is formed. More specifically, the first n-type cladding layer 54 includes an n-type In_y Ga_1-y N (where 0 ≦ y <1). That is, the first n-type cladding layer 414 can be formed of the n-type InGaN described with respect to the first n-type cladding layer 14 in the light emitting device 10 shown in FIG. 1, or formed of n-type GaN. You can also. For the same reason as described for the first n-type cladding layer 14 in the light emitting device 10 shown in FIG. 1, the value of y is preferably in the range of 0 ≦ y ≦ 0.5, more preferably It is in the range of 0 <y ≦ 0.3, most preferably 0 <y ≦ 0.2. For the same reason, the carrier concentration of the first n-type cladding layer 414 is 1 × 10 6.¹⁸/ Cm^Three ~ 1x10²⁰/ Cm^Three It is desirable to be within the range. The thickness of the first n-type cladding layer 414 is not particularly limited, but for the same reason, the active layer 15 and the first n-type cladding layer 414 have a total thickness of 300 angstroms or more. Desirably, it may have a thickness of 1 μm or less.
[0129]
The second n-type cladding layer 424 provided on the first n-type cladding layer serves as an optical confinement layer, has a band gap larger than that of the first n-type cladding layer 414, and is made of aluminum. N-type nitride semiconductor containing n and gallium or n-type GaN. By providing such a second n-type cladding layer 424, the band gap difference with the first n-type cladding layer 414 can be increased, and the light emission efficiency of the light-emitting element can be improved.
[0130]
This second n-type cladding layer 424 is made of n-type Al._g Ga_1-g When N is formed (where 0 <g <1), the value of g is preferably in the range of 0 <g ≦ 0.6. AlGaN has a relatively hard crystal, and if it is larger than 0.6, cracks are relatively likely to occur in the layer despite the presence of the first n-type cladding layer 414, and the light output tends to decrease. Because there is. The g value is most preferably in the range of 0 <g ≦ 0.4.
[0131]
The carrier concentration of the second n-type cladding layer 424 is 5 × 10¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is desirable to be within the range. Its carrier concentration is 5 × 10¹⁷/ Cm^Three Lower than that, the resistivity of AlGaN is particularly high._f, And the luminous efficiency tends to decrease, while the carrier concentration is 1 × 10¹⁹/ Cm^Three This is because the crystallinity of AlGaN is deteriorated and the luminous efficiency is lowered.
[0132]
The second n-type cladding layer 424 can usually be formed with a thickness of 50 Å to 0.5 μm.
[0133]
The n-type contact layer 403 formed as the outermost layer of the n-type semiconductor layer (the layer farthest from the active layer) (formed in contact with the second n-type cladding layer 424 in FIG. 12) , N-type GaN. The n-type contact layer 403 is formed of n-type GaN for the same reason that it is preferable to form the n-type contact layer 13 of n-type GaN in the light emitting device 10 of FIG. Other carrier concentrations, for example, are also preferably the concentrations described as preferred for the n-type contact layer 13 in the light emitting device 10 shown in FIG.
[0134]
The first p-type clad layer 416 provided in contact with the second main surface of the active layer 405 functions as a cap layer, and the first p-type clad in the other forms described so far Like the layer, the active layer is prevented from being decomposed to improve the light emission output of the light emitting element. The first p-type cladding layer 416 is formed of a p-type nitride semiconductor containing aluminum and gallium. It has been found that by providing such a first p-type cladding layer 416, a more excellent LD element can be provided.
[0135]
This first p-type cladding layer 416 is preferably p-type Al._h Ga_1-h N (where 0 <h <1). In this case, the value of h is preferably in the range of 0 <h ≦ 0.6. This is because AlGaN has a relatively hard crystal, and cracks are likely to occur in the layer, which tends to reduce the light output. The h value is most preferably in the range of 0 <h ≦ 0.4.
[0136]
The carrier concentration of the first p-type cladding layer 416 is 1 × 10¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is desirable to be within the range. Its carrier concentration is 1 × 10¹⁷/ Cm^Three Lower than that, the efficiency of hole injection into the active layer 405 tends to decrease and the light emission efficiency tends to decrease, while the carrier concentration is 1 × 10 6.¹⁹/ Cm^Three This is because the crystallinity of AlGaN deteriorates and the luminous efficiency decreases.
[0137]
The first p-type cladding layer 416 can usually be formed with a thickness of 50 Å to 0.5 μm.
[0138]
The second p-type cladding layer 426 provided on the first p-type cladding layer 416 functions as a light guide layer, and is formed of a p-type nitride semiconductor containing indium and gallium or p-type GaN. Yes. More specifically, the first p-type cladding layer 416 is made of p-type In._z Ga_1-z It is desirable to form with N (here, 0 ≦ z <1). For the same reason as described for the first p-type cladding layer 36 in the light emitting element 30 of FIG. 3, the z value is preferably in the range of 0 ≦ z ≦ 0.5, more preferably 0 ≦. It is in the range of z ≦ 0.3, most preferably in the range of 0 ≦ z ≦ 0.2. The first p-type cladding layer 416 may be formed of GaN in the same manner, and functions similarly as a buffer layer. The carrier concentration of the first p-type cladding layer 416 is also 1 × 10 6 for the same reason.¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is desirable to be within the range. Further, the thickness of the first clad layer 416 is not particularly limited, but for the same reason, it is desirable that the total thickness with the active layer 405 is 300 angstroms or more, and the thickness is 1 μm or less. Can do.
[0139]
The third p-type cladding layer 436 provided on the second p-type cladding layer 426 acts as an optical confinement layer, has a band gap larger than that of the second p-type cladding layer 426, and aluminum and gallium. The p-type nitride semiconductor containing is formed. By providing the third p-type cladding layer 436 as described above, the band gap difference with the second p-type cladding layer 426 can be increased, and the light emission efficiency of the light emitting element can be improved.
[0140]
This third p-type cladding layer 436 is preferably p-type Al._i Ga_1-i N (where 0 <i <1). In this case, the value of i is preferably in the range of 0 <i ≦ 0.6. AlGaN has a relatively hard crystal, and if it is larger than 0.6, cracks tend to occur relatively easily in the layer despite the presence of the second p-type cladding layer 426, and the light output tends to decrease. Because there is. The b value is most preferably in the range of 0 <b ≦ 0.4.
[0141]
The carrier concentration of the third p-type cladding layer 436 is 1 × 10¹⁷/ Cm^Three ~ 1x10¹⁹/ Cm^Three It is desirable to be within the range. Its carrier concentration is 1 × 10¹⁷/ Cm^Three Lower than that, the efficiency of hole injection into the active layer 405 tends to decrease and the light emission efficiency tends to decrease, while the carrier concentration is 1 × 10 6.¹⁹/ Cm^Three This is because the crystallinity of AlGaN deteriorates and the luminous efficiency decreases. The third p-type cladding layer 436 can usually be formed with a thickness of 50 Å to 0.5 μm.
[0142]
A p-type contact layer 407 formed as an outermost layer of the p-type semiconductor layer (a layer positioned farthest from the active layer 405) (provided in contact with the third p-type cladding layer 436 in FIG. 12). Is made of p-type GaN. The p-type contact layer 407 is made of p-type GaN for the same reason as that the p-type contact layer 17 in the light emitting device 10 of FIG. 1 is preferably made of p-type GaN. For example, other carrier concentrations are also preferably the concentrations described as preferable in the case of the p-type contact layer 17 in the light emitting device 10 shown in FIG.
[0143]
The substrate 401, the buffer layer 402, the negative electrode 408, and the positive electrode 409 are as described for the substrate 11, the buffer layer 12, the negative electrode 18, and the positive electrode 19 in the light-emitting element 10 shown in FIG. Further, the current confinement layer 440 having the through holes 440a is also as described for the current confinement layer 100 in the light emitting element 90 shown in FIG.
[0144]
According to one aspect of the present invention, an active layer having a quantum well structure made of a nitride semiconductor including first and second main surfaces and containing indium and gallium, on the first main surface of the active layer And an n-type nitride semiconductor layer provided on the second main surface of the active layer, and the p-type nitride semiconductor layer includes: A first p-type layer formed of a p-type nitride semiconductor containing aluminum and gallium and in contact with the second main surface of the active layer, and a p-type provided in contact with the first p-type layer A nitride semiconductor light emitting device comprising a second p-type layer made of GaN is provided. The light emitting device according to this aspect has a special structure in which the second p-type cladding layer 96b and the n-type cladding layer 94 are omitted from the structure of the light-emitting device 90 shown in FIG. 9, and the p-type contact layer 97 is formed of p-type GaN. This is the case. In this case, the n-type contact layer 93 can be most preferably formed of n-type GaN.
[0145]
FIG. 13 shows the fabrication of various nitride semiconductor light emitting devices of the present invention by changing the thickness of the active layer of the quantum well structure, and examining the relationship between the light emission output (relative value) and the thickness of the well layer. The results are shown in a graph. As can be seen from FIG. 13, when the thickness of the well layer of the active layer of the quantum well structure in the nitride semiconductor light emitting device of the present invention is 70 angstroms or less, the light emission output of the light emitting device is remarkably improved. It can also be seen that the light emission output of the light emitting element is further improved when the thickness of the well layer is 50 angstroms or less. Such a tendency has been confirmed not only in the active layer having a single quantum well structure but also in the active layer having a multiple quantum well structure for all the nitride semiconductor light emitting devices of the present invention. It was also confirmed that one of the two clad layers sandwiched was formed of a p-type nitride semiconductor and the other was formed of an n-type nitride semiconductor.
[0146]
Therefore, according to one aspect of the present invention, a quantum well having at least one well layer including a nitride semiconductor containing indium and gallium between an n-type nitride semiconductor layer and a p-type nitride semiconductor layer. There is provided a nitride semiconductor light emitting device comprising an active layer having a structure, wherein the well layer has a thickness of 70 angstroms or less.
[0147]
FIG. 14 shows various nitride semiconductor light emitting devices according to the present invention, in which the thickness of the well layer of the active layer of the multiple quantum well structure is made constant and the thickness of the barrier layer is changed, and the light emission output (relative value). The results of examining the relationship between the thickness of the barrier layer and the barrier layer are shown as a graph. As can be seen from FIG. 14, when the thickness of the barrier layer of the active layer of the quantum well structure in the nitride semiconductor light emitting device of the present invention is 150 angstroms or less, the light emission output of the light emitting device is remarkably improved. It can be seen that when the thickness of the barrier layer is 100 angstroms or less, the light emission output of the light emitting element is further improved. Such a tendency is not only confirmed for all nitride semiconductor light emitting devices of the present invention, but also widely, one of the two cladding layers sandwiching the active layer is formed of a p-type nitride semiconductor and the other is an n-type. It was also confirmed when formed of a nitride semiconductor.
[0148]
FIG. 15 is a graph showing the relationship between the thickness and the light emission output (relative value) when the thickness of the first p-type cladding layer 96a is changed for a light emitting device having a structure similar to the structure shown in FIG. is there. 15 more specifically, in the structure shown in FIG. 9, the n-type GaN contact layer 93 is formed on the sapphire substrate 91 via the GaN buffer layer 92 to a thickness of 4 μm, and the n-type InGaN clad layer 94 is 500 An InGaN active layer 95 having a single quantum well structure is formed to a thickness of 20 Å to a thickness of Å, and a first p-type AlGaN cladding layer 96a is formed thereon with a different thickness. The second p-type AlGaN cladding layer 96b is formed to a thickness of 0.1 μm, the p-type GaN contact layer 97 is formed to a thickness of 1 μm, the negative electrode 98 is formed, and the current confinement layer 100 is provided. It is about the LED element in which the positive electrode 99 is formed.
[0149]
As shown in FIG. 15, when the thickness of the first p-type cladding layer 96a becomes thicker than 1 μm, the light emission output tends to decrease rapidly. Such a thickness is due to cracks in the first p-type cladding layer 96a and deterioration of the crystallinity of the device. FIG. 15 shows that in the case of an LED element, the thickness of the first p-type cladding layer 96a is preferably 10 angstroms (0.001 μm) or more and 1 μm or less. Such a tendency was confirmed for all of the nitride semiconductor light emitting devices of other embodiments of the present invention in which the first p-type cladding layer is formed of AlGaN. In the case of the LD element, the preferable thickness of the first p-type cladding layer is 100 angstroms or more for another reason as described above.
[0150]
FIG. 16 is a graph showing the relationship between the thickness and the light emission output (relative value) when the thickness of the first n-type cladding layer 294a is changed for a light emitting device having a structure similar to the structure shown in FIG. is there. 16 shows more specifically the structure shown in FIG. 10 with the n-type GaN contact layer 93 formed on the sapphire substrate 91 via the GaN buffer layer 92 to a thickness of 4 μm and the second n-type AlGaN cladding layer. 294b is formed to a thickness of 0.1 μm, a first n-type InGaN cladding layer 294a is formed with a different thickness, and an InGaN active layer 95 having a single quantum well structure is further formed thereon to a thickness of 20 Å. Further, the present invention relates to an LED element in which a p-type AlGaN cladding layer 296 is formed to a thickness of 0.1 μm, a negative electrode 98 is formed, and a positive electrode 99 is formed without providing a current confinement layer 100.
[0151]
As can be seen from FIG. 16, when the thickness of the first n-type cladding layer 294a is greater than 1 μm, the light emission output tends to decrease rapidly. This is because the crystallinity of the first n-type cladding layer 294a itself is deteriorated, for example, the crystal becomes black or pits are generated. Even if the thickness of the first n-type cladding layer 294a is less than 30 angstroms, the light emission output tends to decrease. This indicates that the preferred thickness at which the first n-type cladding layer 294a made of InGaN effectively acts as a buffer layer is 30 angstroms or more. Such a tendency was confirmed for all of the nitride semiconductor light emitting devices of other forms of the present invention in which the first n-type cladding layer is formed of InGaN or GaN. As already described, when the first n-type cladding layer 294a is thinner than 10 angstroms, it does not act as a buffer layer, and there are a large number of cracks in the active layer 95 and the cladding layers 294b and 296 formed thereon. As a result, device fabrication becomes difficult and the light emission output is greatly reduced.
[0152]
In the present invention, all of the nitride semiconductors exhibit n-type even when grown without doping with a donor impurity. Most preferably, Si, Ge, Te, S, etc. are used during crystal growth of the nitride semiconductor. Doped with donor impurities. By adjusting the donor impurity concentration, the carrier concentration of the n-type nitride semiconductor layer can be adjusted.
[0153]
In the present invention, each of the p-type nitride semiconductor layers is doped with acceptor impurities such as Mg, Zn, Cd, Ca, Be, and C during the crystal growth of the nitride semiconductor. It is obtained by doing. An even more preferable p-type nitride semiconductor layer can be obtained by annealing the nitride semiconductor layer thus grown by doping the acceptor impurity at a temperature of 400 ° C. or higher. The carrier concentration of the p-type nitride semiconductor layer can be adjusted by adjusting the concentration of the acceptor impurity.
[0154]
The nitride semiconductor light emitting device of the present invention is obtained by using a vapor phase growth method such as MOVPE (metal organic vapor phase epitaxy), MBE (molecular beam vapor phase epitaxy), or HDVPE (hydride vapor phase epitaxy). It can be preferably manufactured by forming each nitride semiconductor layer thereon. For example, using a nitride semiconductor source such as an organic indium compound, an organic gallium compound, an organoaluminum compound, ammonia, etc., forming each nitride semiconductor layer on the substrate by an organic MOVPE method using an impurity source as required, The nitride semiconductor light emitting device of the present invention can be manufactured by forming a positive electrode and a negative electrode.
[0155]
As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to these. For example, the current confinement layer 100 in FIG. 9 can be applied to the semiconductor light emitting device of the present invention in the case of an LD device. The description regarding the indium ratio and carrier concentration for one n-type or p-type InGaN layer applies similarly to other n-type or p-type InGaN layers, and aluminum for one n-type or p-type AlGaN layer. It will be apparent that the explanations for the ratio and carrier concentration apply equally to other n-type or p-type AlGaN layers. As is clear from the above description, the main surface means a surface on which another layer is formed in the nitride semiconductor layer (specifically, the active layer).
[0156]
【Example】
Hereinafter, the present invention will be described based on examples. In the following examples, all nitride semiconductor layers are grown by the MOVPE method.
[0157]
Example 1 First, TMG (trimethylgallium) and NH as source gases_Three Then, a buffer layer made of GaN was grown to a thickness of 500 angstroms at 500 ° C. on the C surface of the sapphire substrate set in the reaction vessel.
[0158]
Next, the temperature is increased to 1050 ° C., and TMG and NH_Three Silane gas was added to the source gas consisting of the above, and an n-type contact layer made of Si-doped n-type GaN was grown to a thickness of 4 μm. The electron carrier concentration of this n-type contact layer is 2 × 10¹⁹/ Cm^Three Met.
[0159]
Subsequently, TMA (trimethylaluminum) was further added to the source gas, and Si-doped n-type Al at 1050 ° C._0.3 Ga_0.7 A second n-type cladding layer made of an N layer was grown to a thickness of 0.1 μm. The electron carrier concentration of this second n-type cladding layer is 1 × 10¹⁹/ Cm^Three Met.
[0160]
Next, the temperature is lowered to 800 ° C., and TMG, TMI (trimethylindium), NH are used as source gases._Three Si-doped n-type In using silane gas_0.01Ga_0.99A first n-type cladding layer made of N was grown to a thickness of 500 angstroms. The electron carrier concentration of the first n-type cladding layer is 5 × 10¹⁸/ Cm^Three Met.
[0161]
Subsequently, TMG, TMI and NH as source gases_Three Non-doped In at 800 ° C._0.05Ga_0.95N was grown to a thickness of 30 Å to form an active layer having a single quantum well structure.
[0162]
Next, the temperature is raised to 1050 ° C., and TMG, TMA, NH are used as source gases._Three And Cp₂ Mg (cyclopentadienyl magnesium) and Mg-doped p-type Al_0.3 Ga_0.7 A second p-type cladding layer made of N was grown to a thickness of 0.1 μm. The hole carrier concentration of this second p-type cladding layer is 1 × 10¹⁸/ Cm^Three Met.
[0163]
Subsequently, TMG, NH3 and Cp as source gases₂ Using Mg, a p-type contact layer made of Mg-doped p-type GaN was grown at 1050 ° C. to a thickness of 0.5 μm. The hole carrier concentration of this p-type contact layer is 5 × 10¹⁹/ Cm^Three Met.
[0164]
Thereafter, the temperature was lowered to room temperature, the wafer was taken out of the reaction vessel, and the wafer was annealed at 700 ° C. to further reduce the resistance of each p-type layer. Next, a mask having a predetermined shape was formed on the surface of the uppermost p-type contact layer, and etching was performed until the surface of the n-type contact layer was exposed. A negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer, and a positive electrode made of Ni and Au was formed on the surface of the p-type contact layer.
[0165]
After the electrodes were formed, the wafer was separated into 350 μm square chips, and an LED element having a directivity characteristic with a half-value angle of 15 degrees was obtained according to a conventional method. This LED element showed blue emission of Vf (forward voltage) of 3.5 V, emission peak wavelength of 415 nm, and emission output of 6 mW at If (forward current) of 20 mA. In addition, the half width of the emission spectrum was 20 nm, and light emission with very good color purity was exhibited.
[0166]
Example 2 Si-doped n-type Al on a sapphire substrate in the same manner as Example 1._0.3 Ga_0.7After growing up to a second n-type cladding layer made of an N layer, non-doped In is formed on the second cladding layer under the same conditions as in Example 1._0.05Ga_0.95N was grown to a thickness of 40 Å to form an active layer having a single quantum well structure.
[0167]
Next, TMG, TMI, NH as source gases are formed on the active layer._Three And Cp2 Mg at 800 ° C. and Mg-doped p-type In_0.01Ga_0.99A first p-type cladding layer made of N was grown to a thickness of 500 angstroms. The hole carrier concentration after annealing of the first p-type layer is 2 × 10¹⁷/ Cm^Three Met.
[0168]
Subsequent growth of the second p-type cladding layer and p-type contact layer, and others were performed in the same manner as in Example 1 to obtain a desired LED element. This LED device had Iff of 20 mA, Vf of 3.5 V, an emission peak wavelength of 410 nm, an emission spectrum half-value width of 20 nm, and an emission output of 5 mW.
[0169]
Example 3 In the same manner as in Example 1, a Si-doped n-type In was formed on a sapphire substrate._0.01Ga_0.99After growing up to the first n-type cladding layer made of N, on the first n-type cladding layer, non-doped In_0.05Ga_0.95N was grown to a thickness of 40 Å to form an active layer having a single quantum well structure.
[0170]
Subsequently, TMG, TMI, NH as source gases_Three And Cp₂ Mg doped p-type In at 800 ° C. using Mg_0.01Ga_0.99A first p-type cladding layer made of N was grown to a thickness of 500 angstroms. The hole carrier concentration after annealing of the first p-type cladding layer is 2 × 10¹⁷/ Cm^Three Met.
[0171]
Next, in the same manner as in Example 1, Mg-doped p-type Al is formed on the first p-type cladding layer._0.3 Ga_0.7 A second p-type cladding layer made of N was grown, and a p-type contact layer made of Mg-doped p-type GaN was grown thereon. Thereafter, in the same manner as in Example 1, a desired LED element was obtained. This LED element is I_fV at 20mA_fThe emission peak wavelength was 3.5 V, the emission peak wavelength was 410 nm, the half width of the emission spectrum was 20 nm, and the emission output was 6 mW.
[0172]
Example 4 Similar to Example 1, on a sapphire substrate, Si-doped n-type Al_0.3 Ga_0.7 After the growth to the second n-type cladding layer made of the N layer, the first n-type cladding layer made of Si-doped n-type GaN is formed to a thickness of 500 angstroms on the second n-type cladding layer. Grown up. The electron carrier concentration of the first n-type cladding layer is 2 × 10¹⁹/ Cm^Three Met.
[0173]
Next, in the same manner as in Example 3, on the first n-type cladding layer 55, non-doped In_{0. 05}Ga_0.95N was grown to a thickness of 40 Å to form an active layer having a single quantum well structure.
[0174]
Next, Mg-doped p-type Al is formed on the active layer in the same manner as in Example 1._0.3 Ga_0.7 A second p-type cladding layer made of N and a p-type contact layer made of Mg-doped p-type GaN were sequentially grown. Thereafter, an LED element was obtained in the same manner as in Example 1. This LED element is I_fV at 20mA_fThe emission peak wavelength was 415 nm, the half width of the emission spectrum was 20 nm, and the emission output was 5 mW.
[0175]
Example 5 The active layer was In_0.2 Ga_0.8 An LED element was produced in the same manner as in Example 1 except that it was formed of N. This LED element is I_fAt 20 mA, V_fBlue light emission of 3.5 V, emission peak wavelength of 455 nm and half width of 20 nm was exhibited, and the light emission output was 5 mW.
[0176]
Example 6 This example was performed in the same manner as Example 1 except for the formation of the active layer. That is, in this example, in order to form the active layer, TMG, TMI, and NH are used as source gases._ThreeNon-doped In at 800 ° C._0.1 Ga_0.9 An N thin film (well layer) was grown to a thickness of 20 Å. Next, In_0.02Ga_0.98An N thin film (barrier layer) was grown to a thickness of 20 Å. Repeat this operation 3 times alternately, and finally In_0.1 Ga_0.9 An N thin film (barrier layer) was grown to a thickness of 20 angstroms to form an active layer having a multiple quantum well structure with a total film thickness of 140 angstroms. The LED element thus obtained is I_fAt 20 mA, V_fBlue light emission of 3.5 V and an emission peak wavelength of 420 nm was exhibited, and the light emission output was 7 mW.
[0177]
Example 7 Indium having a single quantum well structure in which DEZ (diethyl zinc) is used as an acceptor impurity source, silane gas is used as a donor impurity, and Si and Zn are doped as an active layer_0.05Ga_0.95An LED element was fabricated in the same manner as in Example 1 except that the N layer was formed to a thickness of 50 angstroms. This LED element is I_fAt 20 mA, V_fBlue light emission of 3.5 V, an emission peak wavelength of 450 nm, and a half width of 70 nm was exhibited, and the emission output was 3 mW.
[0178]
Example 8 Si-doped n-type In on the n-type contact layer according to the method of Example 1_0.01Ga_0.99First n-type cladding layer made of N, non-doped In_0.05Ga_0.95N active layer, Mg-doped p-type Al_0.3 Ga_0.7 A second p-type cladding layer made of N and a p-type contact layer made of Mg-doped p-type GaN were grown. That is, an LED element was obtained in the same manner as in Example 1 except that the second n-type cladding layer was not formed. This LED element is I_fAt 20 mA, V_fThe emission power was 3.5 m, the emission peak wavelength was 410 nm, and the emission output was 5 mW.
[0179]
Example 9 In the same manner as in Example 1, after growing each semiconductor layer up to the n-type contact layer on the sapphire substrate, the temperature was lowered to 800 ° C. and TMG, TMI, NH as source gases₃Si-doped n-type In using silane gas_0.01Ga_0.99A thin film of N was grown to a thickness of 380 angstroms. Next, the temperature is raised to 1050 ° C., TMG, TMA, NH 3 and silane gas are used as source gases, and Si-doped n-type Al_0.2 Ga_0.8 A thin film of N was grown to a thickness of 390 angstroms. These operations are repeated 20 times, and Si-doped n-type In_0.01Ga_0.99N layer and Si-doped Al_0.2 Ga_0.8 An n-type multilayer film (first multilayer reflective film) was formed by alternately stacking 10 N layers.
[0180]
Next, the second n-type cladding layer, the first n-type cladding layer, the active layer, the first p-type cladding layer, and the second p are formed on the n-type multilayer film in the same manner as in the third embodiment. The mold cladding layer was grown sequentially.
[0181]
Next, the temperature is set to 800 ° C., and TMG, TMI, NH are used as source gases._Three And Cp₂ Mg is used and Mg-doped p-type In is formed on the second p-type cladding layer._0.01Ga_0.99After the N layer is grown to a thickness of 380 Å, the temperature is raised to 1050 ° C., and TMG, TMA, NH are used as source gases._Three And Cp₂ Using Mg gas, Mg doped p-type Al_0.2 Ga_0.8 The N layer was grown to a thickness of 390 angstroms. These operations are repeated until the Mg-doped p-type In_0.01Ga_0.99N layer and Mg-doped p-type Al_0.2 Ga_0.8 A p-type multilayer film (second multilayer reflective film) was formed in which N layers were alternately laminated in ten layers.
[0182]
Next, a p-type contact layer was grown on the p-type multilayer film in the same manner as in Example 1.
[0183]
For the wafer thus obtained, the nitride semiconductor layer was etched in the same manner as in Example 1, and then a mask having a predetermined shape was formed on the surface of the p-type contact layer which is the uppermost layer, and 50 μm was formed on the n-type contact layer. A negative electrode was formed on the p-type contact layer and a positive electrode was formed on the p-type contact layer with a width of 10 μm. When the n-type multilayer film is formed on the n-type contact layer in this way, the horizontal plane on which the negative electrode is formed is below the n-type multilayer film, that is, the substrate side.
[0184]
Next, the surface of the sapphire substrate on which the nitride semiconductor layer is not formed is polished so that the thickness of the substrate is 90 μm, and the M surface of the sapphire substrate surface (the surface corresponding to the side surface of the hexagonal column in the hexagonal system) I scribe. After scribing, the wafer was divided into 700 μm square chips to produce stripe-type LD elements. This LD element has a nitride semiconductor layer surface orthogonal to the stripe-shaped positive electrode as an optical resonance surface. Further, the surface of this LD element is made of SiO except the surface of each electrode.₂It is covered with an insulating film (not shown). Next, this chip was placed on a heat sink, and after wire bonding of each electrode, laser oscillation was attempted at room temperature. The threshold current density was 1.5 kA / cm.²As a result, laser oscillation with an oscillation wavelength of 390 nm was confirmed.
[0185]
Example 10 First, TMG and NH as source gases₃Then, a buffer layer made of GaN was grown to a thickness of 200 angstroms at 500 ° C. on the C surface of the sapphire substrate set in the reaction vessel.
[0186]
Next, the temperature is increased to 1050 ° C. and TMG and NH₃Silane gas was added to the source gas and an n-type contact layer made of Si-doped n-type GaN was grown to a thickness of 4 μm.
[0187]
Next, the temperature is lowered to 800 ° C., TMI is further added to the source gas, and Si-doped n-type In_0.05Ga_0.95A first n-type cladding layer composed of an N layer was grown to a thickness of 500 angstroms.
[0188]
Subsequently, non-doped In on the first n-type cladding layer at 800 ° C._0.2Ga_0.8N was grown to a thickness of 20 Å to form an active layer with a single quantum well structure.
[0189]
Next, the temperature is raised to 1050 ° C., and TMG, TMA, NH are used as source gases.₃And Cp₂Using Mg, Mg-doped p-type Al_0.1Ga_0.9A first p-type cladding layer made of N was grown to a thickness of 0.1 μm.
[0190]
Subsequently, at 1050 ° C., Mg-doped p-type Al_0.3Ga_0.7A second p-type cladding layer made of N was grown to a thickness of 0.5 μm.
[0191]
Subsequently, a p-type contact layer made of Mg-doped GaN was grown to a thickness of 1.0 μm at 1050 ° C.
[0192]
After completion of the reaction, the temperature was lowered to room temperature, the wafer was taken out of the reaction vessel, and the wafer was annealed at 700 ° C. to further reduce the resistance of the p-type layer. Next, etching was performed from the uppermost p-type contact layer until the surface of the n-type contact layer was exposed. After etching, the surface of the p-type contact layer is SiO₂This layer was deposited, and a through hole was provided therein to form a current confinement layer, and a positive electrode made of Ni and Au connected to the p-type contact layer via the through hole was formed on the current confinement layer. A negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer.
[0193]
Next, the surface of the sapphire substrate on which the nitride semiconductor layer was not formed was polished to a thickness of 90 μm, and the M surface of the sapphire substrate was scribed and forcibly cleaved to obtain a laser chip. After providing a dielectric multilayer film on the cleavage plane, the chip was placed on a heat sink, and laser oscillation was attempted at room temperature. The threshold current density was 2.0 kA / cm.²Thus, laser oscillation with an oscillation wavelength of 450 nm was confirmed.
[0194]
Example 11 In the same manner as in Example 10, a GaN buffer layer having a thickness of 200 Å and an n-type contact layer made of n-type GaN were sequentially formed on a sapphire substrate to a thickness of 4 μm.
[0195]
Next, Si-doped n-type Al_0.3Ga_0.7After forming a second n-type cladding layer made of N to a thickness of 0.5 μm, Si-doped n-type In_0.05Ga_0.95A first n-type cladding layer 71 made of N was formed to a thickness of 500 angstroms.
[0196]
Next, non-doped In_0.2Ga_0.8N is grown to a thickness of 20 Å to form an active layer having a single quantum well structure, and Mg-doped p-type Al is formed thereon._0.3Ga_0.7A second p-type cladding layer made of N was formed to a thickness of 0.5 μm, and then a p-type contact layer made of Mg-doped p-type GaN was formed to a thickness of 1 μm.
[0197]
Thereafter, laser oscillation of the obtained LD element was attempted in the same manner as in Example 10. As a result, the threshold current density was 2.0 kA / cm.²Thus, laser oscillation with an oscillation wavelength of 450 nm was confirmed.
[0198]
Example 12 In the same manner as in Example 10, a GaN buffer layer having a thickness of 200 Å and an n-type contact layer made of n-type GaN were sequentially formed on a sapphire substrate to a thickness of 4 μm.
[0199]
Next, Si-doped n-type Al_0.3Ga_0.7After forming a second n-type cladding layer made of N to a thickness of 0.5 μm, Si-doped n-type In_0.05Ga_0.95A first n-type cladding layer made of N was formed to a thickness of 0.1 μm.
[0200]
Next, non-doped In_0.2Ga_0.8NN is grown to a thickness of 20 Å to form an active layer having a single quantum well structure, and Mg-doped p-type Al is formed thereon._0.1Ga_0.9A first p-type cladding layer made of N is grown to a thickness of 0.1 μm, and further Mg-doped p-type Al_0.3Ga_0.7A second p-type cladding layer made of N was grown to a thickness of 0.5 μm, and finally a p-type contact layer made of Mg-doped p-type GaN was grown to a thickness of 0.5 μm.
[0201]
Thereafter, laser oscillation of the obtained LD element was attempted in the same manner as in Example 10. As a result, a threshold current density of 1.0 kA / lower than the threshold current density of the LD elements in Examples 10 and 11 was obtained. cm²Thus, laser oscillation with an oscillation wavelength of 450 nm was confirmed.
[0202]
Example 13 This example was performed in the same manner as Example 12 except for the formation of the first n-type cladding layer and the active layer. That is, as the first n-type cladding layer, Si-doped n-type In_0.05Ga_0.95Instead of N, a Si-doped n-type GaN layer was grown to a thickness of 0.1 μm. In order to form an active layer, non-doped In_0.4Ga_0.6An N well layer is grown to a thickness of 30 angstroms, on which non-doped In_0.08Ga_0.92By repeating the operation of growing the N barrier layer to a thickness of 50 Å, an active layer having a multi-quantum well structure having a total thickness of 190 Å in a five-layer structure of well layer / barrier layer / well layer / barrier layer / well layer is formed. Grown up.
[0203]
For the obtained LD element, laser oscillation was attempted in the same manner as in Example 10. As a result, the threshold current density was 0.9 kA / cm.²The laser oscillation was 500 nm.
[0204]
Example 14 A p-type layer is formed on a sapphire substrate in the same manner as in Example 10 except that after forming the first p-type cladding layer, the p-type contact layer is formed without forming the second p-type cladding layer. Each semiconductor layer up to the contact layer was grown. For the obtained wafer, the resistance of the p-type nitride semiconductor layer was reduced by annealing and the etching from the p-type contact layer to the n-type contact layer was performed, as in Example 10, and then the p-type contact layer was formed on the p-type contact layer. The positive electrode made of Ni and Au was directly formed without forming the current confinement layer, and the negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer. Thus, a desired LED element was obtained. This LED element showed blue light emission with Vf of 3.5 V and an emission wavelength of 450 nm at If20 mA, and the light emission output was 6 mW. In addition, the half-value width of the emission spectrum was as sharp as 20 nm, indicating interband emission.
[0205]
Example 15 In the same manner as in Example 10, each semiconductor layer up to the p-type contact layer was grown on a sapphire substrate. For the obtained wafer, the resistance of the p-type nitride semiconductor layer was reduced by annealing and the etching from the p-type contact layer to the n-type contact layer was performed, as in Example 10, and then the p-type contact layer was formed on the p-type contact layer. The positive electrode made of Ni and Au was directly formed without forming the current confinement layer, and the negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer. Thus, a desired LED element was obtained. This LED element showed blue light emission with Vf of 3.5 V and emission wavelength of 450 nm at If20 mA, and the light emission output was as high as 6 mW. The half-value width of the emission spectrum was as sharp as 20 nm.
[0206]
Example 16 In the same manner as in Example 10, a GaN buffer layer having a thickness of 200 Å and an n-type contact layer made of n-type GaN were sequentially formed on a sapphire substrate to a thickness of 4 μm. This n-type contact layer also functions as a first n-type cladding layer in the LED element of this embodiment.
[0207]
Next, on the n-type contact layer, non-doped In_0.2Ga_0.8N was grown to a thickness of 30 Å to form an active layer having a single quantum well structure.
[0208]
Next, Mg-doped p-type Al_0.1Ga_0.9A first p-type cladding layer made of N was grown to a thickness of 0.05 μm, and a p-type contact layer made of Mg-doped p-type GaN was directly grown to a thickness of 0.5 μm.
[0209]
Thereafter, in the same manner as in Example 14, the resistance of the p-type nitride semiconductor layer was reduced by annealing and the etching from the p-type contact layer to the n-type contact layer was performed. A positive electrode made of Au was directly formed, and a negative electrode made of Ti and Al was formed on the exposed surface of the n-type contact layer. Thus, a desired LED element was obtained. This LED element showed blue light emission with Vf of 3.5 V and an emission wavelength of 450 nm at If20 mA, and the light emission output was as high as 7 mW. The half-value width of the emission spectrum showed sharp interband emission of 20 nm.
[0210]
Example 17 In as an active layer_0.4Ga_0.6An LED element was obtained by the same operation as in Example 16 except that N was grown to a thickness of 50 angstroms. This LED element showed green emission with Vf of 3.5 V and an emission wavelength of 520 nm at If of 20 mA, an emission output of 4 mW, and a half-value width of an emission spectrum of 40 nm.
[0211]
Example 18 An LD element was obtained in the same manner as in Example 3 except for the formation of the active layer and the first p-type cladding layer. That is, in this embodiment, in order to form an active layer, a non-doped In as a well layer on the first n-type cladding layer._0.15Ga_0.85N is grown to a thickness of 25 Å, and a non-doped In as a barrier layer thereon_0.15Ga_0.85The operation of growing N to a thickness of 50 Å was repeated 13 times, and finally the non-doped In as a well layer_0.15Ga_0.85N was grown to a thickness of 25 Å to form an active layer having a multi-quantum well structure with a total thickness of 1000 Å. As the first p-type cladding layer, Al_0.05Ga_0.95N was grown to a thickness of 500 Angstroms. The wafer thus obtained was processed in the same manner as in Example 9 to obtain a desired LD element. This LD element has a threshold current density of 1.0 kA / cm.²The laser oscillation was 415 nm.
[0212]
Example 19 An LD element was obtained in the same manner as in Example 3 except for the formation of the active layer. That is, in this embodiment, in order to form an active layer, a non-doped In as a well layer on the first n-type cladding layer._0.15Ga_0.85N is grown to a thickness of 25 Å, and a non-doped In as a barrier layer thereon_0.05Ga_0.95The operation of growing N to a thickness of 50 angstroms was repeated 26 times, and finally, as a well layer, non-doped In_0.15Ga_0.85N was grown to a thickness of 25 Å to form an active layer having a multi-quantum well structure with a total thickness of 1975 Å. The wafer thus obtained was processed in the same manner as in Example 9 to obtain a desired LD element. This LD element has a threshold current density of 1.0 kA / cm at room temperature.²The laser oscillation was 415 nm.
[0213]
Example 20 One each of the blue LED element obtained in Example 16, the green LED element obtained in Example 17, and a red LED having a light emission output of 3 mW and 660 nm made of a conventional GaAs material or AlInGaP material. A 256 × 256 pixel full-color LED display having a dot of 1 was produced. As a result, the white surface luminance was 10,000 cd, and the color reproduction region was wider than that of the television.
[0214]
【The invention's effect】
As described above in detail, according to the present invention, a nitride semiconductor light emitting device having a high light emission output and a narrow half width of the light emission spectrum is provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing the structure of one embodiment of a nitride semiconductor light emitting device according to the present invention.
FIG. 2 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
FIG. 3 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
FIG. 4 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
FIG. 5 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
FIG. 6 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
FIG. 7 is a perspective view showing an example of the structure of the nitride semiconductor laser device of the present invention.
FIG. 8 is a schematic cross-sectional view showing another structure of the nitride semiconductor laser device of the present invention.
FIG. 9 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
FIG. 10 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
FIG. 11 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
FIG. 12 is a schematic sectional view showing the structure of another embodiment of the nitride semiconductor light emitting device according to the present invention.
FIG. 13 is a graph showing the relationship between the thickness of the well layer of the active layer and the light emission output of the light emitting device in the nitride semiconductor light emitting device of the present invention.
FIG. 14 is a graph showing the relationship between the thickness of the barrier layer of the active layer and the light emission output of the light emitting device in the nitride semiconductor light emitting device of the present invention.
15 is a graph showing the relationship between the thickness of the p-type AlGaN cladding layer and the light emission output of the light emitting device in the nitride semiconductor light emitting device of the present invention. FIG.
FIG. 16 is a graph showing the relationship between the thickness of the n-type InGaN cladding layer and the light emission output of the light emitting device in the nitride semiconductor light emitting device of the present invention.
[Explanation of symbols]
11, 91, 401 ... substrate
13, 93, 403... N-type contact layer
14, 21, 34, 54, 501, 94, 294, 294a, 294b, 414, 412 ... n-type cladding layer
15, 95, 405 ... active layer
16, 36, 41, 56, 502, 96, 96a, 96b, 296, 416, 426, 436 ... p-type cladding layer
17, 97, 407 ... p-type contact layer
18, 98, 408 ... negative electrode
19, 99, 409 ... Positive electrode

Claims (11)

An active layer having a quantum well structure including first and second main surfaces and including a nitride semiconductor containing indium and gallium, and an n-type nitride semiconductor provided on the first main surface of the active layer A semiconductor stacked structure having a layer and a p-type nitride semiconductor layer provided on the second main surface of the active layer,
The n-type nitride semiconductor layer is provided in contact with the first main surface of the active layer, and a first n-type cladding layer made of n-type nitride semiconductor or n-type GaN containing indium and gallium; , Provided at a position farther from the active layer than the first n-type cladding layer, has a larger band gap than the first n-type cladding layer , and has n-type Al _f Ga _1-f N (0 A second n-type cladding layer made of a nitride semiconductor including <f <1) ,
The p-type nitride semiconductor layer includes a first p-type cladding layer provided in contact with the second main surface of the active layer and made of a p-type nitride semiconductor containing aluminum and gallium, The nitride semiconductor light emitting device according to claim 1, wherein the p-type cladding layer has a thickness of 10 angstroms or more and 1.0 μm or less. The p-type nitride semiconductor layer is provided at a position farther from the active layer than the first p-type cladding layer, and is made of p-type GaN or a p-type nitride semiconductor containing indium and gallium. the nitride semiconductor light emitting device according to claim 1, further comprising a type cladding layer. The p-type nitride semiconductor layer has a p-type contact layer on which a positive electrode is formed, and is formed of nitride semiconductors having different compositions between the p-type contact layer and the second p-type cladding layer. 3. The nitride semiconductor light emitting device according to claim 1, further comprising a p-type multilayer light reflecting film. The p-type nitride semiconductor layer, nitride semiconductor light emitting device of any one of claims 1 to 3, characterized in that it has a p-type contact layer is positive electrode is formed. The first n-type clad layer, a nitride semiconductor light emitting device of any one of claims 1 to 4, characterized in that a nitride semiconductor containing indium and gallium. The n-type nitride semiconductor layer has an n-type contact layer on which a negative electrode is formed, and is formed of nitride semiconductors having different compositions between the n-type contact layer and the second n-type cladding layer. the nitride semiconductor light-emitting element described in any one of claims 1 to 5 having n-type multi-layer optical reflecting film to be. 7. The nitride semiconductor according to claim 3 , wherein the multilayer light reflecting film is a nitride semiconductor or GaN in which at least one of the nitride semiconductors constituting the multilayer light reflecting film includes indium and gallium. Light emitting element. 8. The nitride semiconductor light-emitting element according to claim 1, wherein a total film thickness of the first n-type cladding layer and the active layer is not less than 300 μm and not more than 1 μm. Wherein the active layer, the nitride semiconductor light emitting device of any one of claims 1 to 8, characterized in that it constitutes a single quantum well structure consisting of well layers 100 Angstroms thick. Wherein the active layer, one of the claims 1 to 9, characterized in that it constitutes a multiple quantum well structure formed by laminating a indium and gallium consisting nitride semiconductor including a well layer and a barrier layer comprising a nitride semiconductor the nitride semiconductor light emitting device of one of claims. The nitride semiconductor light emitting device according to any one of claims 1 to 10 , wherein the active layer is non-doped.

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