JP2010067792A - Semiconductor light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the deterioration of an active layer. <P>SOLUTION: Cladding layers formed on the active layer 105 are formed to have a double-layer configuration. A hydrogen concentration of one cladding layer closer to the active layer 105 is lower than that of the other cladding layer, and furthermore, at least the cladding layer closer to the active layer 105 has a superlattice structure, so that hydrogen diffusion to the active layer 105 is suppressed, thereby suppressing the deterioration of the active layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device such as a short wavelength semiconductor laser or a light emitting diode.

A group III nitride semiconductor (hereinafter, simply referred to as a nitride-based semiconductor) represented by Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) It is a material that can cover wavelengths from infrared to ultraviolet and is expected to be applied to light emitting and receiving devices.

  As a typical device using a nitride-based semiconductor, a blue-violet laser that oscillates at a wavelength of about 400 nm is known. For example, a contact layer, an n-type cladding layer, an n-type guide layer, an active layer, a p-type electron confinement layer (overflow prevention layer), a p-type guide layer, a p-type cladding layer, and a p-type contact layer are sequentially formed on the substrate. Laser oscillation is performed by applying a voltage between the electrodes (for example, see Patent Document 1 and Patent Document 2).

As another example, n-type GaN, n-type AlGaN cladding layer, n-type GaN guide layer, active layer having a multiple quantum well structure, GaInN intermediate layer, p-type AlGaN electron blocking layer, p-type on a sapphire substrate An AlGaN clad layer and a p-type contact layer are formed to provide a blue-violet laser (see, for example, Non-Patent Document 1).
JP 2000-299497 A JP 2005-101542 A Physica Status Solidi (A), Vol. 192, No. 2, pages 269 to 276, 2002 (Physica Status Solidi (a) 192, No. 2 p. 269-276 (2002))

  In general, Mg is doped to make a nitride semiconductor p-type. At this time, a large amount of H in the raw material is taken together with Mg. Since the hydrogen concentration in the active layer is lower than in the p-type layer, hydrogen diffuses from the p-type layer to the active layer when the semiconductor laser is energized. The diffusion of hydrogen into the active layer causes hydrogen to form a level in the active layer or cause defects. Such levels and defects act as non-radiative recombination centers when energized, leading to an increase in threshold current. An increase in the threshold current causes heat generation, and the active layer tends to deteriorate.

  In view of the above problems, an object of the present invention is to suppress degradation of an active layer.

  In order to achieve the above object, a semiconductor light emitting element according to claim 1 is formed on a first conductive type semiconductor layer formed on the semiconductor substrate and on the first conductive type semiconductor layer. A first conductivity type cladding layer, a first conductivity type guide layer formed on the first conductivity type cladding layer, and an active layer formed on the first conductivity type guide layer An undoped semiconductor layer formed on the active layer, a second conductivity type cap layer formed on the undoped semiconductor layer, and a second layer formed on the second conductivity type cap layer A first cladding layer of the second conductivity type and a second cladding layer of the second conductivity type formed on the first cladding layer of the second conductivity type, and the second conductivity type The first clad layer has a superlattice structure, and the hydrogen concentration is a second clad of the second conductivity type. Characterized in that less than the hydrogen concentration of the layer.

  The semiconductor light emitting device according to claim 2 is the semiconductor light emitting device according to claim 1, wherein the second conductivity type first cladding layer has a dopant concentration of the second conductivity type second cladding layer. It is characterized by being lower than the dopant concentration.

The semiconductor light emitting device according to claim 3 is the semiconductor light emitting device according to claim 2, wherein the dopant is Mg.
The semiconductor light emitting device according to claim 4 is the semiconductor light emitting device according to any one of claims 1 to 3, wherein the second clad layer of the second conductivity type has a superlattice structure. To do.

  6. The semiconductor light emitting device according to claim 5, wherein a semiconductor substrate, a first conductive type semiconductor layer formed on the semiconductor substrate, and a first conductive type formed on the first conductive type semiconductor layer. Type cladding layer, a first conductivity type guide layer formed on the first conductivity type cladding layer, an active layer formed on the first conductivity type guide layer, and the activity An undoped semiconductor layer formed on the layer; a second conductive type cap layer formed on the undoped semiconductor layer; an undoped cladding layer formed on the second conductive type cap layer; A second conductivity type cladding layer formed on the undoped cladding layer, the undoped cladding layer has a superlattice structure, and the hydrogen concentration is lower than the hydrogen concentration of the second conductivity type cladding layer It is characterized by that.

The semiconductor light emitting device according to claim 6 is the semiconductor light emitting device according to claim 5, wherein the dopant of the cladding layer of the second conductivity type is Mg.
The semiconductor light-emitting device according to claim 7 is the semiconductor light-emitting device according to claim 5 or 6, wherein the second conductivity type cladding layer has a superlattice structure.

  As described above, the deterioration of the active layer can be suppressed.

  As described above, the clad layer formed on the active layer has a two-stage configuration, the hydrogen concentration of the clad layer closer to the active layer is lower than the hydrogen concentration of the other clad layer, and at least close to the active layer By making the other cladding layer have a superlattice structure, diffusion of hydrogen into the active layer can be suppressed, and deterioration of the active layer can be suppressed.

Hereinafter, embodiments of the present invention will be described in detail.
In addition, in the following, Al _x Ga _1-x N (0 <x <1) which is a ternary mixed crystal is AlGaN, and In _y Ga _1-y N (0 <y <1) is InGaN, a quaternary mixed crystal. Al _x Ga _1-x In _y N (0 <x <1, 0 <y <1) is appropriately denoted as AlGaInN. Further, as an embodiment, a nitride semiconductor light emitting element formed on a nitride semiconductor substrate will be described as an example, but the present invention can also be applied to a semiconductor light emitting element formed on another semiconductor substrate.
(Embodiment 1)
A semiconductor light emitting device according to the first embodiment of the present invention will be described with reference to the nitride semiconductor light emitting device shown in FIG.

FIG. 1 is a cross-sectional view showing the structure of the nitride semiconductor light emitting device according to the first embodiment.
As shown in FIG. 1, on an GaN substrate 101, an n-type GaN layer 102, an n-type AlGaN cladding layer 103, an n-type GaN guide layer 104, an active layer 105, an undoped GaN guide layer 106, a p-type AlGaN cap layer 107, A first p-type cladding layer 108, a second p-type cladding layer 109, and a p-type GaN layer contact layer 110 are formed.

Si is used for the n-type dopant of the n-type GaN layer 102, the n-type AlGaN cladding layer 103, and the n-type GaN guide layer 104. Although not shown, the active layer 105 includes an InGaN well layer and an InGaN barrier layer. This is a multiple quantum well structure.

Mg is used for the p-type dopant of the p-type AlGaN cap layer 107, the first p-type cladding layer 108, the second p-type cladding layer 109, and the p-type GaN layer contact layer 110.
The first p-type cladding layer 108 and the second p-type cladding layer 109 have a superlattice structure composed of a p-type AlGaN layer and a p-type GaN layer.

In addition, the hydrogen concentration of the first p-type cladding layer 108 is lower than the hydrogen concentration of the second p-type cladding layer 109.
The p-type AlGaN cap layer 107 has a large band gap, and can efficiently keep electrons supplied from the n-type layer in the active layer.

The effects relating to the first p-type cladding layer 108 will be described below.
A p-type cladding layer is formed as a first p-type cladding layer 108 and a second p-type cladding layer 109 sequentially from the side closer to the active layer 105, and the hydrogen concentration of the first p-type cladding layer 108 is changed to the second p-type cladding layer 108. The hydrogen concentration from the second p-type cladding layer 109 to the active layer 105 is less than the first p-type cladding layer 109 because the first p-type cladding layer 108 has a superlattice structure. This is suppressed by the superlattice structure of the mold cladding layer 108.

The reason why hydrogen diffusion is suppressed by the superlattice structure of the first p-type cladding layer 108 is as follows.
That is, the superlattice structure is formed, for example, by repeating a GaN layer and an AlGaN layer each having a thickness of several nm multiple times. The diffusion coefficient for hydrogen differs between the GaN layer and the AlGaN layer. When layers having different diffusion coefficients are combined, even if hydrogen diffuses in a layer having a large diffusion coefficient, diffusion of hydrogen is suppressed in the layer having a small diffusion coefficient. That is, the layer having a small diffusion coefficient serves as a barrier against hydrogen. When layers having different diffusion coefficients are repeatedly formed many times, many barriers against hydrogen are formed, and as a whole, a layer in which hydrogen hardly diffuses can be formed. Since the superlattice structure is formed by repeatedly forming layers having different diffusion coefficients many times, the first p-type cladding layer 108 is a layer that hardly diffuses hydrogen.

  Since the first p-type cladding layer 108 is a layer that hardly diffuses hydrogen and the hydrogen concentration of the first p-type cladding layer 108 is reduced, the second p-type cladding layer 109 is changed to the active layer. Since hydrogen is not diffused to 105 and hydrogen diffusion from the first p-type cladding layer 108 to the active layer 105 is small, the hydrogen concentration in the active layer 105 can be reduced.

  Thus, the hydrogen concentration in the active layer 105 is reduced, thereby increasing the efficiency of light emission recombination of carriers in the active layer 105 and increasing the light emission efficiency of the semiconductor light emitting device. Does not occur, and deterioration of the active layer can be suppressed.

  Note that although the case where the second p-type cladding layer 109 has a superlattice structure is described in this embodiment mode, the superlattice structure is not necessarily required, and a superstructure composed of a p-type AlGaN layer and a p-type GaN layer is not necessarily used. In the case of the lattice structure, the operating voltage can be reduced by setting the film thickness of one period to a film thickness that causes the tunnel effect.

  Further, when the Mg concentration in the first p-type cladding layer 108 is lower than the Mg concentration in the second p-type cladding layer 109, hydrogen is combined with Mg and taken into the semiconductor. By lowering the hydrogen concentration, the hydrogen concentration can be reduced. Then, by reducing the hydrogen concentration in the cladding layer closer to the active layer, diffusion of hydrogen into the active layer can be suppressed.

  In order to express the effect of the present invention, the Mg concentration in the first p-type cladding layer 108 is 1/5 or less, preferably 1/10, of the Mg concentration in the second p-type cladding layer 109. In conjunction with the Mg concentration, the hydrogen concentration in the first p-cladding layer 108 is 1/5 or less, preferably 1/10 or less, of the hydrogen concentration in the second p-type cladding layer 109.

  In the present embodiment, the first p-type cladding layer 108 and the second p-type cladding layer 109 use a superlattice structure composed of a p-type AlGaN layer and a p-type GaN layer, but this combination is limited. Instead, a combination of nitride semiconductors larger than the band gap of the active layer may be used. For example, a superlattice structure composed of p-type AlGaN layers having different compositions or a quaternary mixed crystal of p-type AlGaInN layers may be used.

In addition, since the Mg concentration of the first p-type cladding layer 108 is lowered, the first p-cladding layer 108 has a higher resistance than the second p-type cladding layer 109. Therefore, the film thickness 108 of the first p-type cladding layer is preferably thinner than the film thickness of the second p-cladding layer 109.
Example 1
Specific examples of the semiconductor light-emitting element described in this embodiment will be described below. A cross-sectional view of the nitride semiconductor light emitting device according to this example is as shown in FIG.

  As shown in FIG. 1, an n-type GaN layer 102, an n-type AlGaN cladding layer 103, an n-type GaN guide layer 104, an active layer 105, an undoped GaN guide layer 106, and a p-type AlGaN on a GaN substrate 101 having a thickness of 400 μm. A cap layer 107, a first p-type cladding layer 108, a second p-type cladding layer 109, and a p-type GaN layer contact layer 110 are formed.

The n-type GaN layer 102 has a thickness of 2 μm and is doped with Si at a concentration of 1 × 10 ¹⁹ cm ⁻³ .
The n-type AlGaN cladding layer 103 has a thickness of 2 μm and is doped with Si at a concentration of 1 × 10 ¹⁹ cm ⁻³ . The Al composition is 5%.

The n-type GaN guide layer 104 has a thickness of 100 nm and is doped with Si at a concentration of 5 × 10 ¹⁸ cm ⁻³ .
Although not shown, the active layer 105 has a multiple quantum well structure including an InGaN well layer and an InGaN barrier layer. The In composition of the InGaN well layer is 10%, and the In composition of the InGaN barrier layer is 2%. The number of periods of the multiple quantum structure is 2.

The film thickness of the undoped GaN guide layer is 100 nm.
The p-type AlGaN cap layer 107 has a thickness of 10 nm, an Al composition of 20%, and is doped with Mg at a concentration of 1 × 10 ¹⁹ cm ⁻³ . The hydrogen concentration in the p-type AlGaN cap layer 107 is 1 × 10 ¹⁸ cm ⁻³ .

  Note that the p-type AlGaN cap layer 107 has the above-mentioned Mg concentration and thickness in order to have a role of blocking electrons, but if the film thickness becomes too thick, the amount of hydrogen increases and the effect of the present invention is reduced. 20 nm or less is desirable.

Although not shown, the first p-type cladding layer 108 has a superlattice structure including a p-type AlGaN layer and a p-type GaN layer. The Al composition of the p-type AlGaN layer is 10%, and Mg is doped at a concentration of 5 × 10 ¹⁸ cm ⁻³ . Similarly, the p-type GaN layer is doped with Mg at a concentration of 5 × 10 ¹⁸ cm ⁻³ . Both the p-type AlGaN layer and the p-type GaN layer have a thickness of 2 nm, the number of periods is 20, and the total thickness is 80 nm. The hydrogen concentration in the first p-type cladding layer 108 is 1 × 10 ¹⁷ cm ⁻³ .

Although not shown, the second p-type cladding layer 109 has a superlattice structure including a p-type AlGaN layer and a p-type GaN layer. The Al composition of the p-type AlGaN layer is 10%, and Mg is doped at a concentration of 1 × 10 ¹⁹ cm ⁻³ . Similarly, the p-type GaN layer is doped with Mg at a concentration of 1 × 10 ¹⁹ cm ⁻³ . Both the p-type AlGaN layer and the p-type GaN layer have a thickness of 2 nm, the number of periods is 80, and the total thickness is 320 nm. The hydrogen concentration in the second p-type cladding layer 109 is 1 × 10 ¹⁸ cm ⁻³ .

  Note that the Mg concentration in the first p-cladding layer does not become a steep Mg concentration distribution due to the influence of diffusion from the second p-type cladding layer or the remaining material after forming the p-type AlGaN cap layer. The Mg concentration described here is the average Mg concentration in the layer.

  Although the thickness of the first p-type cladding layer is 80 nm, it is preferably 30 nm or more in order to exhibit the effects of the present invention. However, if the thickness of the first p-type cladding layer is too large, the amount of Mg is small and the resistance becomes high, so 100 nm or less is preferable.

The p-type GaN layer contact layer 110 has a thickness of 30 nm and is doped with Mg at a concentration of 3 × 10 ¹⁹ cm ⁻³ .
As described above, by making the hydrogen concentration of the first p-type cladding layer 108 smaller than the hydrogen concentration of the second p-type cladding layer 109 and making the first p-type cladding layer 108 have a superlattice structure. Since hydrogen is not diffused from the second p-type cladding layer 109 to the active layer 105 and hydrogen is not diffused from the first p-type cladding layer 108 to the active layer 105, the hydrogen concentration in the active layer 105 can be reduced. In addition, no heat is generated due to an increase in threshold current, and deterioration of the active layer can be suppressed.
When an electrode was attached to this semiconductor laser element and a voltage was applied, the lifetime was doubled compared to a semiconductor laser having a Mg concentration of 1 × 10 ¹⁹ cm ⁻³ in the first p-type cladding layer.
(Embodiment 2)
A semiconductor light emitting device according to Embodiment 2 of the present invention will be described with reference to the nitride semiconductor light emitting device shown in FIG.

FIG. 2 is a cross-sectional view showing the structure of the nitride semiconductor light emitting device according to the second embodiment.
As shown in FIG. 2, on the GaN substrate 201, an n-type GaN layer 202, an n-type AlGaN cladding layer 203, an n-type GaN guide layer 204, an active layer 205, an undoped GaN guide layer 206, a p-type AlGaN cap layer 207, An undoped cladding layer 208, a p-type cladding layer 209, and a p-type GaN layer contact layer 210 are formed.

Si is used for the n-type dopants of the n-type GaN layer 202, the n-type AlGaN cladding layer 203, and the n-type GaN guide layer 204.
Although not shown, the active layer 205 includes an InGaN well layer and an InGaN barrier layer.

Further, Mg is used as the p-type dopant for the p-type AlGaN cap layer 207, the p-type cladding layer 209, and the p-type GaN layer contact layer 210.
The p-type AlGaN cap layer 207 has a large band gap, and can efficiently keep electrons supplied from the n-type layer in the active layer 205.

  Although not shown, the undoped cladding layer 208 has a superlattice structure including an undoped AlGaN layer and an undoped GaN layer. Similarly, although not shown, the p-type cladding layer 209 has a superlattice structure composed of a p-type AlGaN layer and a p-type GaN layer.

By forming the undoped cladding layer 208 closer to the active layer than the p-type cladding layer 209, hydrogen diffusion can be suppressed. This will be described below.
The undoped cladding layer 208 has a superlattice structure. The superlattice structure is formed, for example, by repeating a GaN layer and an AlGaN layer each having a thickness of several nm multiple times. The diffusion coefficient for hydrogen differs between the GaN layer and the AlGaN layer. When layers having different diffusion coefficients are combined, even if hydrogen diffuses in a layer having a large diffusion coefficient, diffusion of hydrogen is suppressed in the layer having a small diffusion coefficient. That is, the layer having a small diffusion coefficient serves as a barrier against hydrogen. When layers having different diffusion coefficients are repeatedly formed many times, many barriers against hydrogen are formed, and as a whole, a layer in which hydrogen hardly diffuses can be formed. Since the superlattice structure is formed by repeatedly forming layers having different diffusion coefficients many times, the undoped cladding layer 208 is a layer that hardly diffuses hydrogen.

  Since the undoped cladding layer 208 is a layer that hardly diffuses hydrogen, and the hydrogen concentration of the undoped cladding layer 208 is reduced, the hydrogen concentration in the active layer can be reduced.

  Thus, the hydrogen concentration in the active layer 205 is reduced, thereby increasing the efficiency of light emission recombination of carriers in the active layer and increasing the light emission efficiency of the semiconductor light emitting device. It does not occur and deterioration of the active layer can be suppressed.

  Further, since the undoped cladding layer itself does not contain Mg, the hydrogen concentration is low. Therefore, since the amount of hydrogen to diffuse is small, hydrogen diffusion to the active layer 205 is suppressed, and the active layer 205 is unlikely to deteriorate.

Note that the operating voltage can be reduced by setting the film thickness of one period of the p-type cladding layer 209 to a film thickness that causes a tunnel effect.
In order to express the effect of the present invention, the Mg concentration in the undoped cladding layer 208 is 1/5 or less, preferably 1/10 or less of the Mg concentration in the p-type cladding layer 209. In conjunction with this, the hydrogen concentration in the undoped layer 208 is 1/5 or less, preferably 1/10 or less, of the hydrogen concentration in the p-type cladding layer 209.

  Note that the undoped cladding layer 208 described in this embodiment means a layer that is not intentionally doped. For example, when Mg is mixed from the p-type cladding layer 209 due to Mg diffusion, it is also called undoped. .

  In this embodiment, the p-type cladding layer 209 uses a superlattice structure composed of a p-type AlGaN layer and a p-type GaN layer, but is not limited to this combination, and more than the band gap of the active layer. A combination of large nitride semiconductors may be used. For example, a superlattice structure composed of p-type AlGaN layers having different compositions or a quaternary mixed crystal of p-type AlGaInN layers may be used. Further, it is not necessary to use a superlattice structure. Note that when a superlattice structure is used as the p-type cladding layer 209, current easily flows in the superlattice due to a tunnel effect, so that the resistivity of the p-type cladding layer 209 can be reduced, and the operation of the nitride semiconductor light emitting device Voltage reduction can be expected.

Further, although an undoped cladding layer is used in the present embodiment, high resistance is obtained by undoping. Therefore, it is preferable that the total film thickness is thinner than that of the first p-cladding layer shown in the first embodiment.
(Example 2)
Specific examples of the semiconductor light-emitting element described in this embodiment will be described below. A sectional view of the nitride semiconductor light emitting device according to this example is as shown in FIG.

  On a GaN substrate 201 having a thickness of 400 μm, an n-type GaN layer 202, an n-type AlGaN cladding layer 203, an n-type GaN guide layer 204, an active layer 205, an undoped GaN guide layer 206, a p-type AlGaN cap layer 207, an undoped cladding layer. 208, a p-type cladding layer 209, and a p-type GaN layer contact layer 210 are formed.

The n-type GaN layer 202 has a thickness of 2 μm and is doped with Si at a concentration of 1 × 10 ¹⁹ cm ⁻³ .
The n-type AlGaN cladding layer 203 has a thickness of 2 μm and is doped with Si at a concentration of 1 × 10 ¹⁹ cm ⁻³ . The Al composition is 5%.

The n-type GaN guide layer 204 has a thickness of 100 nm and is doped with Si at a concentration of 5 × 10 ¹⁸ cm ⁻³ .
Although not shown, the active layer 205 has a multiple quantum well structure composed of an InGaN well layer and an InGaN barrier layer. The In composition of the InGaN well layer is 10%, and the In composition of the InGaN barrier layer is 2%. The number of periods of the multiple quantum structure is 2.

The film thickness of the undoped GaN guide layer is 100 nm.
The thickness of the p-type AlGaN cap layer 207 is 10 nm, its Al composition is 20%, and Mg is doped at a concentration of 1 × 10 ¹⁹ cm ⁻³ . The hydrogen concentration in the p-type AlGaN cap layer 207 is 1 × 10 ¹⁸ cm ⁻³ .

  Note that the p-type AlGaN cap layer 207 has the above Mg concentration and thickness in order to have the role of blocking electrons, but if the film thickness becomes too thick, the amount of hydrogen increases and the effect of the present invention is reduced. 20 nm or less is desirable.

Although not shown, the undoped cladding layer 208 has a superlattice structure composed of an undoped AlGaN layer and an undoped GaN layer. The Al composition of the undoped AlGaN layer is 10%. Both the undoped AlGaN layer and the undoped GaN layer have a thickness of 2 nm, the number of periods is 10, and the total film thickness is 40 nm. The hydrogen concentration in the undoped layer is 1 × 10 ¹⁶ cm ⁻³ .

  In addition, the undoped cladding layer 208 described in this example is a layer that is not intentionally doped, and Mg may be mixed in due to Mg diffusion from the p-type cladding layer 209. Called undoped.

Although not shown, the p-type cladding layer 209 has a superlattice structure composed of a p-type AlGaN layer and a p-type GaN layer. The Al composition of the p-type AlGaN layer is 10%, and Mg is doped at a concentration of 1 × 10 ¹⁹ cm ⁻³ . Similarly, the p-type GaN layer is doped with Mg at a concentration of 1 × 10 ¹⁹ cm ⁻³ . Both the p-type AlGaN layer and the p-type GaN layer have a thickness of 2 nm, a period number of 90, and a total film thickness of 360 nm. The hydrogen concentration in the p-type cladding layer 209 is 1 × 10 ¹⁸ cm ⁻³ .

  Moreover, although the thickness of the undoped cladding layer 208 is 40 nm, it is preferably 30 nm or more in order to exhibit the effects of the present invention. However, if the thickness of the undoped cladding layer 208 is too large, the amount of Mg is small and the resistance becomes high, so 100 nm or less is preferable.

The p-type GaN contact layer 210 has a thickness of 30 nm and is doped with Mg at a concentration of 3 × 10 ¹⁹ cm ⁻³ .
As described above, by making the hydrogen concentration of the undoped cladding layer 208 smaller than the hydrogen concentration of the p-type cladding layer 209 and making the undoped cladding layer 208 have a superlattice structure, the p-type cladding layer 209 is changed to the active layer 205. Since hydrogen is not diffused and hydrogen diffusion from the undoped p-type cladding layer 208 to the active layer 205 is small, the hydrogen concentration in the active layer 205 can be reduced, and no heat is generated due to an increase in threshold current. Deterioration can be suppressed.
When an electrode was attached to this semiconductor laser element and a voltage was applied, the lifetime was doubled compared to a semiconductor laser in which Mg was doped to 1 × 10 ¹⁹ cm ⁻³ in the undoped cladding layer.

  In the above embodiment, the case where the first p-type cladding layer 108 or the undoped cladding layer 208 is an AlGaN / GaN superlattice has been described. However, the combination of the group III nitride semiconductor layers constituting the superlattice is not limited to this. Not limited to other combinations of group III nitride semiconductor layers, such as AlGaInN / GaN, AlN / GaN, GaN / InGaN, AlGaN / InGaN, and GaN / InN if possible. Further, for example, the superlattice structure may be formed by repeatedly forming a group III nitride semiconductor layer of nanometer order consisting of three, four, or more layers having different compositions.

  The present invention can suppress degradation of the active layer and is useful for semiconductor light emitting devices such as short wavelength semiconductor lasers and light emitting diodes.

Sectional drawing which shows the structure of the nitride semiconductor light-emitting device concerning Embodiment 1 Sectional drawing which shows the structure of the nitride semiconductor light-emitting device concerning Embodiment 2

Explanation of symbols

101, 201 ... GaN substrate 102, 202 ... n-type GaN layer 103, 203 ... n-type AlGaN cladding layer 104, 204 ... n-type GaN guide layer 105, 205 ... active layer 106, 206 ... undoped GaN guide layer 107, 207 ... p-type AlGaN cap layer 108 ... first p-type cladding layer 208 ... undoped cladding layer 109 ... second p-type cladding layer 209 ... p-type cladding layer 110, 210 ... p-type GaN contact layer

Claims (7)

A semiconductor substrate;
A first conductive type semiconductor layer formed on the semiconductor substrate;
A first conductivity type cladding layer formed on the first conductivity type semiconductor layer;
A first conductivity type guide layer formed on the first conductivity type cladding layer;
An active layer formed on the guide layer of the first conductivity type;
An undoped semiconductor layer formed on the active layer;
A cap layer of a second conductivity type formed on the undoped semiconductor layer;
A first cladding layer of a second conductivity type formed on the cap layer of the second conductivity type;
A second conductivity type second cladding layer formed on the second conductivity type first cladding layer, and the second conductivity type first cladding layer has a superlattice structure. A semiconductor light emitting device, wherein the hydrogen concentration is lower than the hydrogen concentration of the second cladding layer of the second conductivity type.   2. The semiconductor light emitting device according to claim 1, wherein a dopant concentration of the second cladding layer of the second conductivity type is lower than a dopant concentration of the second cladding layer of the second conductivity type.   The semiconductor light-emitting device according to claim 2, wherein the dopant is Mg.   The semiconductor light emitting element according to any one of claims 1 to 3, wherein the second clad layer of the second conductivity type has a superlattice structure. A semiconductor substrate;
A first conductive type semiconductor layer formed on the semiconductor substrate;
A first conductivity type cladding layer formed on the first conductivity type semiconductor layer;
A first conductivity type guide layer formed on the first conductivity type cladding layer;
An active layer formed on the guide layer of the first conductivity type;
An undoped semiconductor layer formed on the active layer;
A cap layer of a second conductivity type formed on the undoped semiconductor layer;
An undoped cladding layer formed on the cap layer of the second conductivity type;
A second conductivity type cladding layer formed on the undoped cladding layer, the undoped cladding layer has a superlattice structure, and the hydrogen concentration is higher than the hydrogen concentration of the second conductivity type cladding layer. A semiconductor light emitting element characterized by being small.   6. The semiconductor light emitting device according to claim 5, wherein the dopant of the second conductivity type cladding layer is Mg.   7. The semiconductor light emitting device according to claim 5, wherein the second conductivity type cladding layer has a superlattice structure.

Images