JPH1093199A - Gallium nitride compound semiconductor light-emitting device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gallium nitride semiconductor light-emitting device of an internal current construction type which has superior reliability. SOLUTION: A gallium nitride compound semiconductor light-emitting device the a substrate 21 and a multilayer structure 200, provided on the substrate 21. The multilayer structure 200 include an active layer 24, a pair of clad layer 23, 25 between which the active layer 24 is provided, a re-evaporation layer 26 formed on the clad layer 25, which is farther from the substrate 21 among the pair of clad layers 23, 25, an internal current constriction layer 27 provided on the re-evaporation layer 26 and having an aperture for constricting a current into a selected region of the active layer 24, and re-growth layers 28, 29 with which the aperture of the internal current constriction layer 27 is filled. The re-evaporation layer 26 functions as an etching stop layer in a process of forming the aperture in the internal current constriction layer 27 and also functions as an over-saturated absorber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride-based compound semiconductor light emitting device capable of emitting light in a blue region to an ultraviolet region and a method of manufacturing the same.

[0002]

2. Description of the Related Art Gallium nitride (GaN) is a group III-V compound semiconductor having a large band gap of 3.4 eV. For this reason, gallium nitride-based semiconductors have been actively studied as materials for light-emitting elements capable of emitting light in a blue region to an ultraviolet region.

A conventional gallium nitride-based compound semiconductor laser will be described with reference to FIG. This semiconductor laser comprises an n-type GaN buffer layer 52, an n-type AlGaN cladding layer 53, a GaN active layer 54, a p-type AlGaN cladding layer 58, an n-type GaN
Internal current blocking layer 57 and p-type GaN contact layer 5
9 are sequentially laminated. On the p-type GaN contact layer 59, a p-side electrode 60 is formed.
The n-side electrode 61 is formed on the back surface of the.

The n-type GaN internal current blocking layer 57 has a stripe-shaped opening (stripe groove) formed by etching. The current flowing from the p-side electrode 60 to the n-side electrode 61 is narrowed by the n-type GaN internal current blocking layer 57 so as to flow vertically in the opening of the n-type GaN internal current blocking layer 57.

[0005] Such a gallium nitride-based compound semiconductor laser is described in, for example, Japanese Patent Application Laid-Open No. 7-249820.

[0006]

When a gallium nitride-based compound semiconductor is etched, there is a problem that etching with excellent selectivity cannot be performed. Therefore, a stripe-shaped opening (stripe groove) is formed in the internal current confinement layer 57.
In the case of performing etching for forming a hole, there is a possibility that even the surface of the cladding layer 58 located below the internal current confinement layer 57 may be etched, and the shape control with good reproducibility is realized unless the etching conditions are strictly adjusted. Did not.

After the stripe-shaped opening is formed in the internal current confinement layer 57 by the etching apparatus, the regrowth layer is formed before the semiconductor layer (cladding layer 59) is regrown so as to fill the opening. The underlying surface (the surface of the cladding layer 59) is exposed to the atmosphere. The semiconductor surface exposed to the atmosphere is oxidized, and contaminants adhere to that portion. Even if a regrowth layer was formed on such an exposed surface, a regrowth interface having good crystal quality could not be obtained.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to control the shape of an internal current confinement layer (internal current blocking layer) with good reproducibility, and to provide a high-quality reproduction. An object of the present invention is to provide a highly reliable gallium nitride-based compound semiconductor light emitting device having a growth interface and a method for manufacturing the same.

[0009]

The gallium nitride based compound semiconductor light emitting device of the present invention is a gallium nitride based compound semiconductor light emitting device comprising a substrate and a laminated structure provided on the substrate. The laminated structure includes an active layer, a pair of clad layers sandwiching the active layer, a re-evaporation layer formed on a clad layer of the pair of clad layers remote from the substrate, An internal current confinement layer having an opening for confining current in a selected region of the active layer; and a regrowth layer covering the internal current confinement layer. Functions as an etch stop layer in the step of forming the opening in the internal current confinement layer, thereby achieving the above object.

In a preferred embodiment, the cladding layer is formed of Al _x Ga ₁ -xN (0 ≦ x <1), and the active layer is formed of In _y Ga _{1 -yN} (0 ≦ y ≦ 1, x = 1). When 0, y>
0), and the reevaporation layer is In _z Ga _1-z N (z
≠ 0), wherein the internal current confinement layer is Al _w Ga
_1-w N (0 ≦ w ≦ 1).

In a preferred embodiment, I
The n mixed crystal ratio z is equal to or higher than the In mixed crystal ratio y of the active layer, and the reevaporation layer functions as a saturable absorber.

A method for manufacturing a gallium nitride based compound semiconductor light emitting device according to the present invention comprises a substrate, an active layer, a pair of clad layers sandwiching the active layer, and a clad layer of the pair of clad layers which is farther from the substrate. A re-evaporation layer formed on the layer, an internal current confinement layer provided on the re-evaporation layer and having an opening for confining current in a selected region of the active layer;
A method of manufacturing a gallium nitride-based compound semiconductor light emitting device having a regrowth layer covering the internal current confinement layer, wherein the step of forming the reevaporation layer on a clad layer remote from the substrate; Forming the internal current confinement layer on the evaporation layer; and selectively forming a part of the internal current confinement layer such that the etching rate for the re-evaporation layer is lower than the etching rate for the internal current confinement layer. Etching,
An etching step for partially exposing the surface of the re-evaporation layer, a step for evaporating the exposed part of the re-evaporation layer, and forming a regrown layer to fill the opening of the internal current confinement layer. And the above-mentioned object is achieved.

In a preferred embodiment, the cladding layer is formed of In _x Ga _1-x N (0 ≦ x <1), and the active layer is formed of In _y Ga _1-y N (0 ≦ y ≦ 1, x = 1). When 0, y> 0)
And the reevaporation layer is formed of In _z Ga _{1 -zN} (0 <z ≦
1), and the internal current confinement layer is formed of In _w Ga _{1 -w} N
(0 ≦ w ≦ 1).

In a preferred embodiment, the step of evaporating the exposed portion of the reevaporation layer is performed at 500 to 750 ° C.
The heat treatment is performed at a temperature within the range described above.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. In the specification of the present application, “gallium nitride-based semiconductor” means that gallium nitride (GaN) is partially replaced by another gallium nitride (GaN).
Semiconductors replaced by group element, for example, Ga _s Al _t I
n _1-st N (0 <s ≦ 1, 0 ≦ t <1, 0 <s + t ≦
1), and includes a semiconductor in which a part of each constituent atom is replaced with a dopant atom or the like, or a semiconductor to which another impurity is added.

In this specification, the term “semiconductor light emitting device”
Include light emitting diodes and semiconductor lasers.

Embodiment 1 A gallium nitride-based compound semiconductor laser device will be described as a first embodiment of a gallium nitride-based compound semiconductor light-emitting device according to the present invention with reference to FIG.

FIG. 1 schematically shows a cross section of a gallium nitride-based compound semiconductor laser device of this embodiment. This semiconductor laser device has an n-type SiC
Substrate 1 and semiconductor laminated structure 100 provided on substrate 1
And a pair of electrodes 10 and 11 for supplying a current (drive current) necessary for light emission.

Hereinafter, the configuration of the semiconductor multilayer structure 100 will be described in detail.

The semiconductor multilayer structure 100 has an n-type GaN buffer layer (having a thickness of 0.5 to
About 1 μm) 2, n-type Al _0.1 Ga _0.9 N cladding layer (about _{0.7 to} 1 μm in thickness) 3, non-doped In _0.32 Ga
_0.68 N active layer (thickness 30 ~ 800Å) 4, Mg doped p
Type Al _0.1 Ga _0.9 N cladding layer (thickness 0.1-0.3μ)
m) 5, Mg-doped InN re-evaporation layer (thickness 30 mm)
6. n-type GaN internal current confinement layer (thickness 0.3 to 0.5 μm)
m) 7, an Mg-doped p-type Al _0.1 Ga _0.9 N cladding layer (about 0.7 to 1 μm in thickness) 8 and an Mg-doped p-type GaN contact layer (0.5 to 1 μm in thickness) 9.

The n-type GaN internal current confinement layer 7 is a selected region of the non-doped In _0.32 Ga _0.68 N active layer 4 (in this embodiment, a stripe-shaped region extending in the resonator length direction).
It has an opening for narrowing the current. The width of the stripe-shaped opening is determined so as to adjust the transverse mode of laser oscillation.

The portion of the Mg-doped InN reevaporation layer 6 corresponding to the opening of the n-type GaN internal current confinement layer 7 evaporates during the manufacturing process. Therefore, Mg-doped p-type Al
_{The 0.1} Ga _0.9 N cladding layer 8 is formed through the opening through the M
contacting the g-doped p-type Al _0.1 Ga _{0. 9} N cladding layer 5.

A p-side electrode 10 is formed on the upper surface of the Mg-doped p-type GaN contact layer 9, and an n-side electrode 11 is formed on the back surface of the substrate 1. A voltage is applied to the electrodes 10 and 11 from a current supply circuit (not shown), and a current flows from the p-side electrode 10 to the n-side electrode 11 in the semiconductor multilayer structure 100. At this time, since the current is blocked by the n-type GaN internal current confinement layer 7, the current flows through the opening of the n-type GaN internal current confinement layer 7 from top to bottom while being constricted. Thus, laser oscillation in a controlled transverse mode occurs, and laser light having a wavelength in the blue to ultraviolet range is obtained.

Hereinafter, a method of manufacturing the semiconductor laser shown in FIG. 1 will be described with reference to FIGS.

In this embodiment, the gallium nitride based semiconductor layer is formed by metal organic chemical vapor deposition (MOCVD).
Method). Specifically, ammonia (NH ₃ ) is used as a group V raw material, and trimethylgallium (TMG), trimethylaluminum (TMA), or trimethylindium (TMIn) is used as a group III raw material. H ₂ and N ₂ are used as carrier gases. As the P-type dopant, biscyclobenzyldienyl magnesium (Cp2Mg) is used, and as the N-type dopant, monosilane (SiH ₄ ) is used.

In order to perform the first crystal growth by the MOCVD method, an n-type SiC substrate 1 is
After being placed on the susceptor of the D apparatus, the substrate temperature was set to 1200
The surface of the substrate 1 is cleaned by raising the temperature to about ° C.

Next, the temperature of the n-type SiC substrate 1 is set to 1000
After cooling down to about ° C, an n-type GaN buffer layer (thickness of about 0.5 to 1 μm) 2 and an n-type Al _0.1 Ga _0.9 N clad layer (thickness of 0.7 to 1 μm) are provided on the n-type SiC substrate 1. Grow 3). Thereafter, the substrate temperature is set to 800 to 85.
The temperature is lowered to about 0 ° C. to grow a non-doped In _0.32 Ga _0.68 N active layer (thickness: 50 to 800 °). Next, the substrate temperature was raised to about 1000 ° C., and Mg-doped Al _0.1
Ga _0.9 N cladding layer (thickness: about 0.1 to 0.3 μm)
Grow 5. After lowering the substrate temperature to about 800 to 850 ° C., the Mg-doped InN re-evaporation layer 6 is grown to a thickness of 30 °. Next, after raising the substrate temperature to about 1000 ° C., the n-type GaN internal current confinement layer (thickness of 0.3 to
0.5 μm) 7 is grown. Thus, the structure shown in FIG. 4A is obtained.

In growing these semiconductor layers, the substrate 1 is
It is performed continuously without taking out from the growth chamber of the CVD apparatus.

Next, once the substrate 1 on which the semiconductor layer is laminated is taken out of the growth chamber, the substrate 1 is subjected to ordinary photolithography (and etching) as shown in FIG.
A mask 12 as shown in (b) is formed on the n-type GaN internal current confinement layer 7. This mask is made of SiO _x or Si
N _x (x is an integer of about 1 to 2) or a photoresist. This mask 12 has a stripe-shaped opening 13.

Next, as shown in FIG. 4C, a portion of the n-type GaN internal current confinement layer 7 which is not covered with the mask 12 is selectively etched by a dry etching technique. Upon etching, the underlying Mg-doped InN re-evaporation layer 6 functions as an etch stop layer. Therefore, the surface 14 of the Mg-doped InN re-evaporation layer 6
Etching can be stopped easily and with good reproducibility at the time when is exposed. In order to sufficiently fulfill the function as an etch stop layer, the thickness of the Mg-doped InN re-evaporation layer 6 needs to be about 10 ° or more. However, if the thickness is too large, there is a problem that the absorption of the laser light increases rapidly and the luminous efficiency deteriorates. Therefore, it is preferable to make the thickness smaller than about 100 °.

The above-mentioned etching is performed, for example, by ECR-R
Mg-doped InN using a gas such as BCl ₃ / Ar or CCl ₂ F ₂ / Ar by 1BE (reactive ion beam etching using electron cyclotron resonance), RlBE, or RIE (reactive ion etching).
The process is performed until the surface of the reevaporation layer 6 is exposed. Thereafter, the mask 12 is removed with a hydrofluoric acid-based etchant or an organic solvent (FIG. 4D).

For the second crystal growth (regrowth), the substrate 1 is set on the susceptor of the MOCVD apparatus again. In a N ₂ and NH ₃ atmosphere, at a substrate temperature of about 550 ° C.,
The exposed portion 15 of the Mg-doped InN layer 6 is re-evaporated to expose the surface of the Mg-doped Al _0.1 Ga _0.9 N clad layer 5 as shown in FIG.

The important aspect of the present invention is that constituting the re-evaporation layer 6 from a high vapor pressure _{In z Ga 1-z N (} 0 <z ≦ 1). For this reason, high-temperature annealing (for example, annealing at 1000 ° C. or more) for re-evaporation becomes unnecessary, and about 5
Re-evaporation is realized at a sufficiently low substrate temperature of about 00 to 750 ° C. For example, when an InN layer having a thickness of 30 ° is used as the re-evaporation layer, the base can be exposed by a heat treatment of about 5 minutes at a temperature of about 550 ° C.

At such a relatively low temperature, the underlying Al _0.1 Ga _0.9 N cladding layer does not evaporate, so that A
The surface morphology and crystal quality of the l _0.1 Ga _0.9 N cladding layer are not degraded. Further, the exposed portion of the reevaporation layer 6 can be selectively removed by a simple heat treatment without using a special etching solution, so that the base surface and the like are not contaminated.

Further, since the re-evaporation step can be easily performed in the MOCVD apparatus, the exposed surface of the Al _0.1 Ga _0.9 N clad layer is not affected by oxidation by the air or the like.
Maintain a good clean surface in the OCVD equipment.

In the MOCVD apparatus, following the re-evaporation step, a second crystal growth is performed. More specifically, after raising the substrate temperature to about 1000 ° C., FIG.
As shown in (f), an Mg-doped Al _0.1 Ga _0.9 N cladding layer (about 0.7 to 1 μm in thickness) 8 and a Mg-doped GaN contact layer (about 0.5 to 1 μm in thickness) 9 are grown. Since this regrowth is performed on the above-mentioned clean surface in a good state, a good regrowth layer having excellent crystallinity is formed.

After removing the substrate 1 from the MOCVD apparatus, thermal annealing was performed at 800 ° C. in an N ₂ atmosphere.
This changes the Mg-doped layer to p-type. Thereafter, as shown in FIG. 4 (g), a p-side electrode 10 is formed on the p-type GaN contact layer 9, and an n-side electrode 11 is formed on the back surface of the n-type SiC substrate 1.

Embodiment 2 Referring to FIG. 2, another gallium nitride based compound semiconductor laser device will be described as a second embodiment of the gallium nitride based compound semiconductor light emitting device of the present invention.

FIG. 2 schematically shows a cross section of the gallium nitride-based compound semiconductor laser device of this embodiment. As shown in FIG. 2, this semiconductor laser device includes a sapphire substrate 21 and a semiconductor laminated structure 2 provided on the substrate 21.
00 and a pair of electrodes 30 and 31 for supplying a current required for light emission.

Hereinafter, the configuration of the semiconductor multilayer structure 200 will be described.

In the semiconductor laminated structure 200, GaN, AIN, or Al _0.1 Ga _0.9 N
It has a buffer layer (about 500 to 2 μm) 22a. On this first buffer layer 22a, an n-type GaN buffer layer (having a thickness of 0.5 to
22b, n-type Al _0.1 Ga _0.9 N cladding layer (thickness of about _{0.7 to} 1 μm) 23, non-doped In _0.32
Ga _0.68 N active layer (thickness 30 to 800 °) 24, Mg-doped p-type Al _0.1 Ga _0.9 N clad layer (thickness 0.1 to
0.3 μm) 25, Mg-doped InN re-evaporation layer (thickness 30 °) 26, n-type Al _0.1 Ga _0.9 N internal current confinement layer (thickness 0.3-0.5 μm) 27, Mg-doped p-type Al
_0.1 Ga _0.9 N cladding layer (about 0.7-1 μm thick) 2
8, and an Mg-doped p-type GaN contact layer (thickness: 0.5 to 1 μm) 29 are formed.

An n-type Al _0.1 Ga _0.9 N internal current confinement layer 27
Has an opening for confining current in a selected region (in the present embodiment, a stripe-shaped region extending in the resonator length direction) of the non-doped In _0.32 Ga _0.68 N active layer 24. The width of the stripe-shaped opening is determined so as to adjust the transverse mode of laser oscillation.

As in the first embodiment, Mg-doped In
The portion of the N re-evaporation layer 26 corresponding to the opening of the n-type Al _0.1 Ga _0.9 N internal current confinement layer 27 evaporates during the manufacturing process. Therefore, Mg-doped p-type Al _0.1 Ga _0.9 N
A part of the cladding layer 28 is in contact with the Mg-doped p-type Al _0.1 Ga _0.9 N cladding layer 25 through the opening.

A p-side electrode 30 is formed on the upper surface of the Mg-doped p-type GaN contact layer 29, and an n-side electrode 31 is formed on a partially exposed portion of the n-type GaN buffer layer 22b. A voltage is applied to the electrodes 30 and 31 from a current supply circuit (not shown), and a current flows from the p-side electrode 30 to the n-side electrode 31 in the laminated structure. At this time, the current because it is blocked by the n-type Al _0.1 Ga _0.9 N internal current constricting layer 27, a current flows from the upper opening of the n-type Al _0.1 Ga _0.9 N internal current constricting layer 27 down.

Hereinafter, a method for manufacturing the semiconductor laser device of FIG. 2 will be described with reference to FIGS.

The same M as in the MOCVD method used in Example 1
In order to perform the first crystal growth by the OCVD method, the sapphire substrate 21 is placed on the susceptor of the MOCVD apparatus, and the substrate temperature is reduced to 1 in an N ₂ or H ₂ gas atmosphere.
By increasing the temperature to about 200 ° C., the surface of the substrate 21 is subjected to a cleaning process.

Next, the temperature of the substrate 21 is set at 500 ° C. to 650 ° C.
Temperature down to about ℃, GaN, AlN, or Al _0.1 G
a _0.9 N buffer layer 22a is grown. Substrate temperature 1
After raising the temperature to about 000 ° C., an n-type GaN buffer layer (about 0.5 to 1 μm in thickness) 22b is formed on the buffer layer 22a.
And n-type Al _0.1 Ga _0.9 N clad layer (thickness 0.7 to
23 is grown. Then, the substrate temperature is set to 8
The temperature is lowered to about 00 to 850 ° C., and the non-doped In _0.32 Ga
_{A 0.68} N active layer (thickness 30-800 Å) 24 is grown. Next, the substrate temperature is raised to about 1000 ° C.
Doped Al _0.1 Ga _0.9 N cladding layer (thickness 0.1 to 0.
25 is grown (about 3 μm). 800-8 substrate temperature
After cooling to about 50 ° C., the Mg-doped InN re-evaporation layer 2
6 is grown to a thickness of 30 °. Next, the substrate temperature was set at 10
After the temperature is raised to about 00 ° C., an n-type Al _0.1 Ga _0.9 N internal current confinement layer (thickness: 0.3 to 0.5 μm) 27 is grown. Thus, the structure shown in FIG. 5A is obtained.

For the growth of these semiconductor layers, the substrate 21 is
It is performed continuously without taking out from the growth chamber of the OCVD apparatus.

Next, once the substrate 21 on which the semiconductor layer is laminated is taken out of the growth chamber, the mask 3 as shown in FIG.
2 is formed on the n-type Al _0.1 Ga _0.9 N internal current confinement layer 27. The mask 32 is formed of SiO _x or SiN _x (x is an integer of about 1 to 2) or a photoresist. The mask 32 has a stripe-shaped opening 33.

Next, as shown in FIG. 5C, a portion of the n-type Al _0.1 Ga _0.9 N internal current confinement layer 27 which is not covered with the mask 32 is selectively etched by a dry etching technique. I do. When etching, M
The g-doped InN reevaporation layer 26 functions as an etch stop layer. Therefore, when the surface 34 of the Mg-doped InN re-evaporation layer 26 is exposed, the etching can be stopped easily and with good reproducibility.

The above-mentioned etching is performed, for example, by ECR-R
Mg-doped InN using a gas such as BCl ₃ / Ar or CCl ₂ F ₂ / Ar by 1BE (reactive ion beam etching using electron cyclotron resonance), RlBE, or RIE (reactive ion etching).
The process is performed until the surface of the reevaporation layer 26 is exposed. Thereafter, the mask 32 is removed with a hydrofluoric acid-based etchant or an organic solvent.

For the second crystal growth (regrowth), the substrate 21 is set again on the susceptor of the MOCVD apparatus. In a N ₂ and NH ₃ atmosphere, at a substrate temperature of about 550 ° C.,
The exposed portion 35 of the Mg-doped InN layer 26 is re-evaporated,
As shown in FIG. 5D, Mg-doped Al _0.1 Ga _0.9 N
The surface of the cladding layer 25 is exposed.

Following the re-evaporation step, a second crystal growth is performed. After raising the substrate temperature to about 1000 ° C,
As shown in FIG. 5E, Mg-doped Al _0.1 Ga _0.9 N
Cladding layer (about 0.7 to 1 μm thick) 28 and Mg
Doped GaN contact layer (thickness of about 0.5-1 μm)
Grow 29. Since this regrowth is performed on the above-mentioned clean surface in a good state, a good regrowth layer having excellent crystallinity is formed.

After removing the substrate 21 from the MOCVD apparatus, thermal annealing at 800 ° C. is performed in an N ₂ atmosphere.
This changes the Mg-doped layer to p-type. Thereafter, as shown in FIG. 5F, the n-type GaN buffer layer 2
The above laminated structure is partially etched until a part of 2b is exposed.

Next, as shown in FIG.
A p-side electrode 30 is formed on the N contact layer 29, and an n-type G
The n-side electrode 31 is formed on the partially exposed portion of the aN buffer layer 22b.
To form

As described above, according to the production method of the present invention,
Since the re-evaporation layer that can be easily removed by heat treatment at a relatively low temperature is used as the etch stop layer, the processing of the internal current confinement layer can be performed with good reproducibility.

(Embodiment 3) Still another semiconductor laser device will be described as a third embodiment of the gallium nitride based compound semiconductor light emitting device of the present invention with reference to FIG.

FIG. 3 schematically shows a cross section of the gallium nitride-based compound semiconductor laser device of this embodiment. As shown in FIG. 3, the semiconductor laser device includes a sapphire substrate 21 and a semiconductor laminated structure 3 provided on the substrate 21.
00 and a pair of electrodes 30 and 31 for supplying a current (drive current) necessary for light emission.

Hereinafter, the configuration of the semiconductor multilayer structure 300 will be described.

In the semiconductor laminated structure 300, GaN, AIN or Al _0.1 Ga _0.9 N
It has a buffer layer (thickness of about 500 to 2 μm) 22a. On the first buffer layer 22a, the substrate 2
The n-type GaN buffer layer (about 0.5 to 1 μm thick) 22b, the n-type Al _0.1 Ga _0.9 N clad layer (about 0.7 to 1 μm thick) 23, and the non-doped In _0.32 Ga _0.68 N active layer (thickness 30 ~ 800mm) 2
4, Mg-doped p-type Al _0.1 Ga _0.9 N cladding layer (about _0.1 to 0.3 μm thick) 25, Mg-doped In _0.32 G
a _0.68 N re-evaporation layer (thickness: about 100 mm) 36, n-type Ga
N internal current confinement layer (thickness of about 0.3 to 0.5 μm) 3
7, Mg-doped p-type Al _0.1 Ga _0.9 N cladding layer 28,
And an Mg-doped p-type GaN contact layer 29 are formed.

A p-side electrode 30 is formed on the upper surface of the Mg-doped p-type GaN contact layer 29, and an n-side electrode 31 is formed on a part of the n-type GaN buffer layer 22b which is exposed. A voltage is applied to the electrodes 30 and 31 from a current supply circuit (not shown), and a current flows from the p-side electrode 30 to the n-side electrode 31 in the laminated structure.

In this embodiment, Mg-doped p-type Al
Mg-doped In _0.32 formed between the _0.1 Ga _0.9 N cladding layer 25 and the n-type GaN internal current confinement layer 37.
The Ga _0.68 N re-evaporation layer 36 also functions as a saturable absorber. In order to function as a saturable absorber, the mixed crystal ratio m of In in the Mg-doped In _m Ga _1-m N re-evaporation layer 36 is set to be equal to or higher than the mixed crystal ratio of In in the active layer 24. This is very important. According to such a configuration, a laser causing self-sustained pulsation can be obtained, and a low-noise gallium nitride-based compound semiconductor laser can be obtained.

For manufacturing the semiconductor laser, for example, the method described in the second embodiment can be used. Below, FIG.
The manufacturing method will be described with reference to (a) to (g).

First, in order to perform the first crystal growth, the sapphire substrate 21 is placed on the susceptor of the MOCVD apparatus, and then the substrate temperature is reduced to 1 in an N ₂ or H ₂ gas atmosphere.
By increasing the temperature to about 200 ° C., the surface of the substrate 21 is subjected to a cleaning process.

Next, the temperature of the substrate 21 is set at 500 ° C. to 650 ° C.
Temperature down to about ℃, GaN, AlN, or Al _0.1 G
a _0.9 N buffer layer 22a is grown. Substrate temperature 1
After the temperature was raised to about 000 ° C., an n-type GaN buffer layer 22 b and an n-type Al _0.1 Ga _0.9 N
The cladding layer 23 is grown. Thereafter, the substrate temperature is set to 80
The temperature is lowered to about 0 to 850 ° C., and the non-doped In _0.32 Ga
_{A 0.68} N active layer 24 is grown. Next, the substrate temperature was set at 10
The temperature is raised to about 00 ° C., and a Mg-doped Al _0.1 Ga _0.9 N clad layer 25 is grown. Substrate temperature 800 to 850
After cooling to about ° C, Mg-doped In _0.32 Ga _0.68 N
The reevaporation layer 36 is grown. Next, the substrate temperature is set to 1000
After the temperature is raised to about ℃, the n-type GaN internal current confinement layer 37
Grow. Thus, the structure shown in FIG. 6A is obtained.

For the growth of these semiconductor layers, the substrate 21 is
It is performed continuously without taking out from the growth chamber of the OCVD apparatus.

Next, once the substrate 21 on which the semiconductor layer is laminated is taken out of the growth chamber, the mask 3 as shown in FIG.
2 is formed on the n-type GaN internal current confinement layer 37. The mask 32 is formed of SiO _x or SiN _x (x is an integer of about 1 to 2) or a photoresist.
The mask 32 has a stripe-shaped opening 33.

Next, as shown in FIG. 6C, a portion of the n-type GaN internal current confinement layer 37 which is not covered with the mask 32 is selectively etched by a dry etching technique. When etching, dope Mg
The In _0.32 Ga _0.68 N re-evaporation layer 36 functions as an etch stop layer. Therefore, Mg-doped In _0.32 Ga
_When the surface 34 of the _0.68 N reevaporation layer 36 is exposed, the etching can be stopped easily and with good reproducibility.

The above etching is performed, for example, by ECR-R
Mg-doped In using a gas such as BCl ₃ / Ar or CCl ₂ F ₂ / Ar by lBE (reactive ion beam etching using electron cyclotron resonance), RlBE, or RIE (reactive ion etching).
_{The process} is performed until the surface of the _0.32 Ga _0.68 N reevaporation layer 36 is exposed. Thereafter, the mask 32 is removed with a hydrofluoric acid-based etchant or an organic solvent.

For the second crystal growth (regrowth), the substrate 21 is set again on the susceptor of the MOCVD apparatus. In a N ₂ and NH ₃ atmosphere, at a substrate temperature of about 550 ° C.,
The exposed portion 35 of the Mg-doped In _0.32 Ga _0.68 N re-evaporation layer 36 is re-evaporated to expose the surface of the Mg-doped Al _0.1 Ga _0.9 N clad layer 25 as shown in FIG.

Following the re-evaporation step, a second crystal growth is performed. After raising the substrate temperature to about 1000 ° C,
As shown in FIG. 6E, Mg-doped Al _0.1 Ga _0.9 N
Cladding layer 28 and Mg-doped GaN contact layer 2
Grow 9 Since this regrowth is performed on the above-mentioned clean surface in a good state, a good regrowth layer having excellent crystallinity is formed.

After removing the substrate 21 from the MOCVD apparatus, thermal annealing is performed at 800 ° C. in an N ₂ atmosphere.
This changes the Mg-doped layer to p-type. Thereafter, as shown in FIG. 6F, the n-type GaN buffer layer 2
The above laminated structure is partially etched until a part of 2b is exposed.

Next, as shown in FIG.
A p-side electrode 30 is formed on the N contact layer 29, and an n-type G
The n-side electrode 31 is formed on the partially exposed portion of the aN buffer layer 22b.
To form

In each of the above embodiments, the InN layer is used as the re-evaporation layer, but the In _z Ga _{1 -z} N (0 <
If z ≦ 1), substantially the same effect can be obtained. However, considering the easiness of re-evaporation, In _z Ga _{1 -z} N
The preferred range of the In composition z of (0 <z ≦ 1) is 0.5
It is 1.0 or less. Further, when importance is attached to the function of the etch stop, the preferable range of the In composition z is 0.5 or more and 1.0 or less. When considered comprehensively, the In composition z
Is preferably 0.32 or more and 1.0 or less.

[0075]

According to the present invention, since the re-evaporation layer functioning as an etch stop layer is disposed below the internal current confinement layer, the step of selectively removing a part of the internal current confinement layer can be performed in the following manner. Without damaging the underlying cladding layer,
Shape control with good reproducibility becomes possible. In particular, by forming a re-evaporation layer having a high vapor pressure _{In z Ga lz N (0 <} z ≦ 1), after finishing it serves as an etch stop layer is lower exposed portions of the re-evaporation layer substrate It can be re-evaporated at a temperature, thereby partially exposing the surface of the cladding layer located below the re-evaporation layer. Therefore, the surface of the cladding layer located below the re-evaporation layer
The exposure can be performed by a method excellent in controllability and reproducibility without using a special etching solution.

Since the step of exposing the surface of the clad layer by evaporation of the re-evaporation layer can be performed in a semiconductor thin film growth apparatus such as an MOCVD apparatus, a re-growth layer can be formed following the step. . For this reason, the exposed surface of the clad layer is not affected by oxidation or the like by the atmosphere and is kept in a clean and defect-free state, so that a good regrown layer is formed thereon.

Further, since the Mg-doped InGaN re-evaporation layer also functions as a saturable absorber, a low-noise gallium nitride-based compound semiconductor laser can be obtained.

As described above, according to the present invention, an internal current confinement type gallium nitride based semiconductor light emitting device having excellent reliability is provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a gallium nitride-based compound semiconductor laser according to the present invention.

FIG. 2 is a schematic cross-sectional view of another gallium nitride based compound semiconductor laser according to the present invention.

FIG. 3 is a schematic cross-sectional view of still another gallium nitride-based compound semiconductor laser according to the present invention.

FIGS. 4A to 4G are process cross-sectional views illustrating a method for manufacturing the gallium nitride-based compound semiconductor laser of FIG.

5 (a) to 5 (g) are process cross-sectional views illustrating a method for manufacturing the gallium nitride based compound semiconductor laser of FIG. 2;

6 (a) to 6 (g) are process cross-sectional views showing a method for manufacturing the gallium nitride-based compound semiconductor laser shown in FIG. 3;

FIG. 7 is a schematic cross-sectional view of a conventional gallium nitride-based compound semiconductor laser.

[Explanation of symbols]

1 n-type SiC substrate 21 Sapphire substrate 51 n-type 3C-SiC substrate 22a GaN, AlN, AlGaN buffer layer 2, 22b n-type GaN buffer layer 3, 23 n-type AlGaN cladding layer 4, 24 non-doped InGaN active layer 54 GaN active layer 5, 8, 25, 28 p-type AlGaN cladding layer 6, 26 p-type InN re-evaporation layer 36 p-type InGaN re-evaporation layer (saturated absorber) 7 n-type GaN internal current confinement layer 27 n-type Al _0.1 Ga _0.9 N internal Current confinement layer 37 n-type GaN internal current confinement layer 9, 29 p-type GaN contact layer 10, 30 p-side electrode 11, 31 n-side electrode 12, 32 etching mask 13, 33 etching mask opening 14, 34 p-type InN Surface of re-evaporation layer 15, 35 Re-evaporated part of p-type InN re-evaporation layer

Claims (6)

[Claims] 1. A gallium nitride-based compound semiconductor light emitting device comprising a substrate and a laminated structure provided on the substrate, wherein the laminated structure comprises: an active layer; and a pair of a pair sandwiching the active layer. A cladding layer, a reevaporation layer formed on the cladding layer of the pair of cladding layers that is farthest from the substrate, and a current confined to a selected region of the active layer provided on the reevaporation layer. An internal current confinement layer having an opening for performing the operation, and a regrowth layer covering the internal current confinement layer, wherein the reevaporation layer forms the opening in the internal current confinement layer. A gallium nitride-based compound semiconductor light emitting device that functions as an etch stop layer. 2. The method according to claim 1, wherein the cladding layer is formed of Al _x Ga ₁ -xN (0 ≦
x <1), the active layer is formed of In _y Ga _1-y N (0 ≦ y ≦ 1, y> 0 when x = 0), and the reevaporation layer is formed of In _z Ga _1-z The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein the internal current confinement layer is formed of N (z ≠ 0), and the internal current confinement layer is formed of Al _w Ga _1-w N (0 ≦ w ≦ 1). 3. The reevaporation layer according to claim 2, wherein the In mixed crystal ratio z of the reevaporation layer is equal to or higher than the In mixed crystal ratio y of the active layer, and the reevaporation layer functions as a saturable absorber. The gallium nitride-based compound semiconductor light-emitting device according to the above. 4. A substrate, an active layer, a pair of clad layers sandwiching the active layer, a re-evaporation layer formed on a clad layer of the pair of clad layers remote from the substrate, A gallium nitride-based system including an internal current confinement layer provided on the evaporation layer and having an opening for confining current in a selected region of the active layer, and a regrown layer covering the internal current confinement layer A method of manufacturing a compound semiconductor light emitting device, comprising: a step of forming the reevaporation layer on a clad layer remote from the substrate; a step of forming the internal current confinement layer on the reevaporation layer; A portion of the internal current confinement layer is selectively etched such that the etching rate for the re-evaporation layer is lower than the etching rate for the current confinement layer, thereby partially exposing the surface of the re-evaporation layer. An etching step; A method of manufacturing a gallium nitride-based compound semiconductor light emitting device, comprising the steps of: evaporating an exposed portion of a light emitting layer; and forming the regrown layer so as to fill the opening of the internal current confinement layer. . 5. The method according to claim 1, wherein the cladding layer is formed of In _x Ga ₁ -xN (0 ≦
x <1), the active layer is formed of In _y Ga _1-y N (0 ≦ y ≦ 1, y> 0 when x = 0), and the reevaporation layer is formed of In _z Ga _1-z 5. The gallium nitride-based compound semiconductor light-emitting device according to claim 4, wherein the internal current confinement layer is formed from In _w Ga _{1 -wN} (0 ≦ w ≦ 1). Production method. 6. The method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to claim 4, wherein in the step of evaporating the exposed portion of the reevaporation layer, a heat treatment is performed at a temperature in the range of 500 to 750 ° C.