JP2001223434A - Nitride-based semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a gallium nitride-based semiconductor laser device which has an optical wave guide structure having a good refractive index profile and has a high efficiency and a high yield, which have been impossible to achieve in the conventional nitride-based compound semiconductor laser device. SOLUTION: The gallium nitride-based semiconductor laser comprises a substrate, lower clad layer of a first conductivity type, active layer, upper clad layer of a second conductivity type, and contact layer of the second conductivity type, which are laminated in this order. In this semiconductor laser, a ridge stripe geometry extended in the resonator direction is constituted of the upper clad layer of the second conductivity type and the contact layer of the second conductivity type, a protective film is formed on the side face of the ridge stripe geometry, and a p type electrode is formed on the upper face of the ridge stripe geometry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gallium nitride based semiconductor laser device and a method of manufacturing the same.

[0002]

2. Description of the Related Art Gallium nitride-based compound semiconductors are wide gap semiconductors and have a direct transition type band structure, and are therefore expected to be applied to light emitting devices having emission wavelengths in the blue to ultraviolet range.

[0003] Among these applications, GaInN is used as an active layer G.
Double hetero-type light-emitting diodes using aAlN as a cladding layer have been put to practical use, and developments have been actively made toward the practical use of semiconductor laser devices. Such a semiconductor laser device is manufactured using a sapphire or SiC substrate by a metal organic chemical vapor deposition method (hereinafter, referred to as MOCVD method) or a molecular beam epitaxial method (hereinafter, referred to as MBE method). FIGS. 10 and 11 are schematic views of a conventionally manufactured compound semiconductor laser device.

[0004] A compound semiconductor laser device shown in FIG. 10 has a buffer layer 10 for lattice matching on a substrate 101.
2, a lower cladding layer 103, an active layer 104, and an upper cladding layer 105 are sequentially formed. Incidentally, reference numeral 1 in the figure
06 is a current blocking layer, 107 and 108 are metal electrodes.
The compound semiconductor laser device shown in FIG.
In the opening 06, current is injected by the metal electrode 108 in contact with the cladding layer 105. In the device having such a structure, the current injected near the opening of the current blocking layer 106 spreads in the upper cladding layer 105 in the horizontal direction.
6 is wider than the width of the opening. Further, in this element structure, since a structure for confining light in the horizontal direction is not formed, the current blocking layer 106 is formed by a difference in gain between a portion where current is injected and a portion where current is not injected.
An optical waveguide is formed below the opening in such a manner that the light intensity is concentrated (hereinafter referred to as an electrode stripe structure).

In the semiconductor laser device shown in FIG. 11, a buffer layer 152, a lower cladding layer 153,
Active layer 154, upper cladding layer 155, current blocking layer 15
6, a contact layer 157 is sequentially formed. Incidentally, reference numerals 158 and 159 in the figure indicate metal electrodes. In the compound semiconductor laser device shown in FIG. 11, the current element layer 156 is placed in the semiconductor multilayer structure, and the opening limits the current injection width. Even in this case, the current spreads in the clad layer 155 in the horizontal direction, but the spread of the current can be reduced because the thickness of the clad layer 155 can be reduced as compared with the case of FIG. Further, in the semiconductor laser device structure of FIG. 11, since the current blocking layer 156 is made of a material that absorbs light emitted from the active layer, the current blocking layer 156 has a lower portion of the opening and a lower portion other than the opening. The structure has a refractive index difference in the horizontal direction, and an optical waveguide is formed (hereinafter, referred to as an internal current confinement structure).

[0006]

However, the above-mentioned conventional compound semiconductor laser device and the manufacturing method have the following problems. In the compound semiconductor laser device having the electrode stripe structure as shown in FIG. 10, as described above, current spreading in the cladding layer 105 occurs in the horizontal direction, so that the efficiency of current injection into the active layer is low and the oscillation threshold is high. Furthermore, since an optical waveguide having a refractive index distribution in the horizontal direction is not built, the wavefront in the horizontal direction has a large bend, and the astigmatism is as large as several tens of μm or more, so that good light-collecting characteristics cannot be obtained. However, there is a problem that the light source is not suitable for a light source of a pickup for an optical disk.

On the other hand, in the case of a compound semiconductor laser device having an internal current confinement structure as shown in FIG. 11, the above problem has been solved. In other words, the efficiency of current injection into the active layer 154 is good, the oscillation threshold can be lowered, and an optical waveguide having a refractive index distribution in the horizontal direction is built. Therefore, the horizontal wavefront has a small bend and the astigmatic difference is small. Smaller than several μm,
Since it is suitable as a light source of a pickup for an optical disc because of obtaining good light-collecting characteristics, it is possible to use an AlGaAs or Al
It is well known that GaInP-based infrared to red light emitting semiconductor lasers are generally widely used.

However, no suitable chemical etching solution has been found in gallium nitride-based materials, and the current blocking layer required to form the internal current confinement structure is 0.5 μm.
It takes several tens of hours or more to remove about m to 1 μm by wet etching, and it is practically impossible to manufacture a compound semiconductor laser device having a structure as shown in FIG.

Further, when a dry etching method is used for a gallium nitride-based material, a practical etching of several thousand degrees per minute is possible. Is as large as about ± 25%.
Therefore, in a nitride-based compound semiconductor laser device having a standard structure as shown in FIG. 11 in which the thickness of the upper cladding layer 155 is 0.2 μm and the thickness of the current blocking layer 156 is 1 μm, the current blocking layer 156 is striped. When the contact layer 157 and the upper clad layer 15 are
At the interface of No. 5, a portion where the current blocking layer 156 is not completely removed by etching or a portion where etching has progressed too much and the upper cladding layer 155 has been removed are formed on the same plane. Therefore, in the gallium nitride-based compound semiconductor laser device having the structure of FIG. 11, poor current injection, deterioration of the crystal quality of the active layer, and the like occur.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a highly efficient gallium nitride compound semiconductor laser device having an optical waveguide structure having a refractive index distribution in the horizontal direction, and a gallium nitride compound semiconductor laser having a high production yield. An object of the present invention is to provide a method for manufacturing a device.

[0011]

According to the present invention, there is provided a nitride semiconductor laser device comprising: a substrate; a first conductivity type lower cladding layer; an active layer; a second conductivity type upper cladding layer;
A gallium nitride-based semiconductor laser having a conductive type contact layer in this order, comprising a ridge stripe extending in the resonator direction with the second conductive type upper cladding layer and the second conductive type contact layer, A protection film is formed on the side surface of the ridge stripe, and a p-type electrode is formed on the entire upper surface of the ridge stripe.

Further, according to the present invention, there is provided a nitride-based semiconductor laser device comprising: a conductive substrate; a first conductive type lower clad layer; an active layer; a second conductive type upper clad layer; In a gallium nitride based semiconductor laser having a conductive type contact layer, the second conductive type upper cladding layer and the second conductive type contact layer have a ridge stripe extending in a resonator direction, and a side surface of the ridge stripe. A p-type electrode on the entire upper surface of the ridge stripe, an n-type electrode on the back surface of the conductive substrate,
It is characterized by being formed respectively.

[0013] The semiconductor device is characterized in that a protective film is provided on the surface of the ridge stripe-shaped second conductive type upper cladding layer.

Further, in the nitride semiconductor laser device according to the present invention, the first conductive type lower cladding layer is preferably made of AlGa.
N, GaN, GaAlInN, the active layer is made of InGaN or GaN, and the second conductive type upper cladding layer is made of AlGaN, GaN, G
aAlInN.

Further, in the nitride semiconductor laser device according to the present invention, the active layer is a single quantum well layer or a multiple quantum well layer made of InGaN.

[0016]

(Embodiment 1) As an embodiment according to the present invention, a GaInN active layer is formed on a SiC substrate.
A method of manufacturing a compound semiconductor laser device having a double hetero junction having a GaAlN cladding layer and a ridge guide structure by using dry etching will be described.

FIG. 1 shows the structure of a gallium nitride based semiconductor laser device according to the present invention. Reference numeral 1 denotes a 6H-SiC substrate,
2 is an AlN buffer layer, 3 is an n-type GaN layer, 4 is an n-type G
a _{0. 85} Al _0.15 N lower cladding layer, 5 Ga _0.75 an In
_0.25 N active layer, p-type Ga _{0. 85} Al _0.15 N upper cladding layer 6, p-type GaN contact layer 7, 9 Al ₂ O ₃ protective film, 10 is a p-side electrode, 11 denotes an n-side electrode . (Less than,
In this embodiment, GaAlN and GaInN
Represents the composition described above. The symbol d indicates the thickness of the p-type GaAlN upper cladding layer 6 outside the ridge stripe shape.

The semiconductor laser device shown in FIG. 1 is characterized in that the upper cladding layer has a ridge stripe shape.

FIG. 2 is a cross-sectional view showing a manufacturing process of the gallium nitride compound semiconductor semiconductor laser according to the present invention. First, from the n-type (0001) silicon (Si) surface as a substrate,
The surface of the 6H-SiC substrate 1 turned off 5 degrees in the 1120> direction was polished and then oxidized to remove the damaged layer on the surface. This 6H-SiC substrate is
After setting the reactor in a VD reactor and replacing the reactor with hydrogen, the temperature was increased to 1500 ° C. while flowing hydrogen and ammonia, and maintained for 10 minutes.
The surface of the C substrate 1 is cleaned.

Next, the substrate temperature is lowered to 1050 ° C.
When stabilized at 050 ° C, trimethylaluminum (hereinafter, referred to as
Notated as TMA. ) At a flow ^{rate of} 3 × 10 ^-5 mol / min and 5 liters / min of ammonia, followed by treatment for 5 minutes to grow an AlN buffer layer 2 of about 0.1 μm. FIG. 2A is a cross-sectional view after the above steps are completed.

Next, trimethylgallium (hereinafter referred to as TMG)
It is written. ) At 3 × 10 ^-5 mol / min and ammonia at 5 / min
A liter of silane gas is flowed at a flow rate of 0.3 cc / min as a Si doping material for 15 minutes, and the n-type GaN layer 3 for lattice matching is grown by treating for 15 minutes.

Next, in addition to ammonia and TMG, TM
A: 6 × 10 ^-6 mol / min, silane gas: 0.3 cc / min
Then, an n-type GaAlN lower cladding layer 4 of about 1 μm is grown by a treatment for 25 minutes. The electron density of this layer is 2 × 1
0 ¹⁸ cm ^-3 .

Next, the supply of TMG, TMA and silane gas is stopped, and the temperature is lowered to 800.degree. Temperature 800
When stabilized at ° C., TMG and trimethylindium (hereinafter referred to as TMI) were flowed at 4 × 10 ^-4 mol / min,
Then, a 10-nm GaInN active layer 5 is grown by performing the processing for seconds.

Next, the supply of TMG and TMI is stopped, and the temperature is raised to 1050 ° C. again. Temperature is 1050 ° C
When stabilized, 5 × 10 ^-6 mol of Cp ₂ Mg (cyclopentadienylmagnesium) is flowed per minute as a doping material for TMG, TMA and p-type, and treated for 25 minutes to obtain an approximately 1 μm Mg-doped GaAlN upper clad. The layer 6 is grown.

Next, supply of only TMA is stopped, and a 300-nm Mg-doped GaN contact layer 7 is grown for 7.5 minutes. FIG. 2 is a cross-sectional view after the above process is completed.
(B).

Mg Doping of the Semiconductor Device Fabricated Above
Electron beam evaporation on the GaN contact layer 7
1 μm wide stripe S by photolithography process
iO _TwoA film 8 is formed. The cross-sectional view after the above process is completed
2 (c).

Next, in a reactive ion etching apparatus,
Striped S with etching gas mainly containing chlorine
The Mg-doped GaN layer contact layer 7 and the Mg-doped GaAlN upper cladding layer 6 other than the portion where the iO ₂ film 8 was formed were etched. In this etching step, the Mg-doped GaAlN upper cladding layer 6 has a thickness of 0.1 mm.
The etching time is adjusted so that the etching is completed while leaving 2 μm. Here, the etching condition is DC
By setting the bias to 200 V and the RF power to 300 W, the Mg-doped GaN layer contact layer 7 and Mg
The etching rate of the doped GaAlN upper cladding layer 6 is 3000 ° / min.
Seconds went. Under the above conditions, the DC bias is ± 50 V, R
The F power was ± 50 W, and the variation in the etching rate was about ± 10%.

Next, a heat treatment at about 700 ° C. is performed in a nitrogen atmosphere for about 20 minutes to lower the resistance of the Mg-doped GaAlN upper cladding layer 6 and the GaN contact layer 7 to make them p-type. By this treatment, the hole concentration of both layers is about 1 × 10 ¹⁸ c
m ^-3 . FIG. 2D is a cross-sectional view after the above process is completed.
Shown in

Next, an Al ₂ O ₃ film 9 is formed as a protective film on the side surface of the ridge stripe shape by an electron beam evaporation method. Thereafter, the stripe-shaped SiO ₂ film 8 having a width of 1 μm is removed with hydrofluoric acid. After washing with water and drying, the p-side electrode 10 of the Au / Ni laminated film is entirely formed on the upper surface of the ridge type stripe by a vacuum evaporation method.

Next, the mirror surface of the laser resonator is formed. A 500 μm wide SiO ₂ film is used as a mask in a direction orthogonal to the electrode stripes of the Au / Ni laminated film 10 as a mask.
Electron beam evaporation is performed at intervals of 0 μm.

Next, a Si having a stripe of 50 μm
The wafer on which the O ₂ film is formed is introduced into a reactive ion etching apparatus, and a gallium nitride-based semiconductor layer at the opening of the SiO ₂ film is formed up to the AlN buffer layer 2 to form a reflective mirror. Etching is removed by an etching method. Further, the 6H-SiC substrate 1 is polished and processed to a thickness of about 100 μm, and the SiO ₂ film used as a mask is removed.

Next, an n-side electrode 11 is formed on the entire back surface of the SiC substrate 1. Through the above steps, a GaAlInN-based semiconductor laser device is formed. FIG. 2E shows a cross-sectional view after the above steps.

Finally, the laser device is divided into chips by scribing and mounted on a package by an ordinary method to complete a laser device.

FIG. 5 shows the correlation between the upper cladding layer thickness d outside the ridge stripe shape and the horizontal radiation angle. It can be seen that the horizontal radiation angle characteristics increase sharply as the thickness d of the upper cladding layer decreases. FIG. 5 shows that when the thickness d of the upper cladding layer is larger than 0.2 μm, the spread of the horizontal radiation angle is suppressed.

The element manufactured by the manufacturing method by dry etching shown in the first embodiment typically has a current of 50 mA.
The laser oscillation was observed at a current of, and as the emission angle characteristics, an ellipticity of 2 with a vertical divergence of 24 ° and a horizontal divergence of 12 ° was obtained, but the oscillation threshold was 3
0 mA to 100 mA, spread angle in horizontal direction is 10 ° to 2
It was within 3 °. The astigmatic difference was 1 to 5 μm.

In this embodiment, an example of a blue-emitting semiconductor laser device using a GaInN layer as an active layer and GaAlN as a cladding layer has been described. However, the present invention is not limited to this combination. Or a GaN active layer / GaAlN clad layer, or a combination of GaAlInN-based quaternary compounds as long as the combination allows laser oscillation.

(Embodiment 2) FIG. 3 shows a blue light emitting compound semiconductor laser device manufactured by a selective growth method to form a ridge stripe shape. 1 are given the same reference numerals. Symbol 21a is p-type GaAlN
The upper cladding layer 21b is a p-type GaAl which is selectively grown.
The N upper cladding layer 23 is an SiO ₂ protective film. This compound semiconductor laser device is characterized in that it has a ridge stripe shape, and that a protective film is formed of two layers of silicon oxide and aluminum oxide on the surface of the p-type GaAlN upper cladding layer having the ridge stripe shape.

Next, a method of manufacturing the compound semiconductor laser device of the second embodiment will be described.

First, fabrication is performed in the same manner as in FIG. 2A of the first embodiment. This step is shown in FIG.

Next, similarly to the first embodiment, the n-type GaN layer
3, n-type GaAlN lower cladding layer 4, GaInN activity
Layer 5 is laminated, the temperature is raised to 1050 ° C. and ammonia is added
5 liters per minute, 3 x 10 TMG per minute^-FiveMole, TMA
6 × 10 per minute^-6Mole and Cp _TwoMg 5 × 10 per minute^-6Mo
0.2μm Mg doping by treating for 5 minutes
The grown GaAlN upper cladding layer 21a is grown. Less than
The above process is shown in FIG.

Next, the Mg-doped GaAlN upper clad
An electron beam evaporation method and photolithography are applied to the surface of the pad layer 21a.
Having an opening 22 with a width of 1 μm by the lithography method
iO _TwoA film 23 is formed. The above steps are shown in FIG.
You.

Thereafter, S having an opening 22 having a width of 1 μm is formed.
iO_TwoGallium nitride based compound semiconductor with film 23 formed
MO on wafer with double heterostructure
Introduced to the CVD equipment, and the reactor of the MOCVD equipment was
After flushing with hydrogen, flush with hydrogen and ammonia.
And raise the temperature to 1050 ° C,
Once stabilized, add 3x10 TMG per minute^-FiveMol, TMA per minute
6 × 10^-6Mol, Cp _TwoMg 5 × 10 per minute^-6Mol, a
Run ammonia at 5 liters per minute and treat for 20 minutes.
About 0.8 μm of Mg in the opening 22 having a width of 1 μm.
Growing a doped GaAlN upper cladding layer 21b;
You. This growth is selectively performed only in the opening 22.
The SiO 2 except for the opening 22_TwoOn the film 23, a semiconductor layer
Does not grow.

Next, the supply of only TMA is stopped, and a 0.5 μm Mg-doped GaN contact layer 7 is grown for 10 minutes. As described above, a portion other than the SiO ₂ film 23 is selectively grown to form a ridge stripe shape serving as an optical waveguide. FIG. 4D shows a cross-sectional view after the above steps.

Next, a heat treatment at about 700 ° C. is performed in a nitrogen atmosphere for about 20 minutes to lower the resistance of the Mg-doped GaAlN upper cladding layers 21 a and 21 b and the GaN contact layer 7 to p-type. By this treatment, the hole concentration of both layers is about 1
× 10 ¹⁸ cm ^-3 .

Next, Al is used as a protective film on the surface other than the upper surface of the ridge stripe by using a usual photolithography method.
_{A 2} O ₃ film 9 is formed by an electron beam evaporation method, and the p-side electrode 1 of the Au / Ni laminated film is formed only on the upper surface of the ridge stripe shape.
0 is entirely formed by a vacuum evaporation method. FIG. 4E shows a cross-sectional view after the above steps are completed. The SiO ₂ film used for the selective growth is left, and an Al ₂ O ₃ film 9 is formed thereon.
, The surface protection of the p-type GaAlN upper cladding layer can be simplified to a two-layer structure.

Next, the mirror surface of the laser resonator is formed. A 500 μm wide SiO ₂ film is used as a mask in a direction orthogonal to the electrode stripes of the Au / Ni laminated film 10 as a mask.
Electron beam evaporation is performed at intervals of 0 μm.

Next, a Si having a stripe of 50 μm
The wafer on which the O ₂ film is formed is introduced into a reactive ion etching apparatus, and the GaAlInN-based semiconductor layer at the opening of the SiO ₂ film is subjected to normal reactive ion beam etching until the AlN buffer layer 2 to form a reflection mirror. Is removed by etching. Further, the 6H-SiC substrate 1 is polished and processed to a thickness of about 100 μm, and the SiO ₂ film used as a mask is removed.

Finally, an n-side electrode 11 is formed on the entire back surface of the SiC substrate 1, divided into chips by scribing, and mounted on a package by a normal method, thereby completing a nitride-based laser device.

When a current was applied to a compound semiconductor laser device manufactured by using the above-mentioned selective growth method, typically,
Laser oscillation at a blue wavelength of 432 nm was observed at a threshold current of 40 mA, and as an emission angle characteristic, an ellipticity of 2 with a vertical divergence of 24 ° and a horizontal divergence of 12 ° was obtained. Was. The astigmatic difference was 1 to 5 μm.

In the device manufactured in this embodiment, the oscillation threshold is 38 mA to 42 mA, and the divergence angle in the horizontal direction is 1
The variation was in the range of 1.5 ° to 12.5 °, indicating that the control of the thickness of the cladding layer outside the ridge stripe was superior to the characteristics of the first embodiment. The film thickness controllability of the GaAlN cladding layer by the MOCVD method was about ± 2% in a φ2 inch substrate surface.

In the compound semiconductor laser device according to the second embodiment, since the protective film of the upper cladding layer outside the ridge stripe is formed of two layers of aluminum oxide and silicon oxide, the protective effect is high. The element life is improved.

In the present embodiment, as the substrate, 5 substrates are set in the <1120> direction from the n-type (0001) silicon (Si) surface.
Although the example using the 6H-SiC substrate 1 which has been turned off has been described, it can also be realized using a p-type SiC substrate. In this case, it is necessary to reverse the conduction type of each semiconductor layer described in the embodiment. is there. The same effect was obtained by using a substrate that was not turned off. Furthermore, not limited to 6H-SiC,
Even if an H-SiC substrate and a 2H-SiC substrate are used, the same or better effects can be obtained.

The ridge stripe shape does not need to be formed from the upper cladding layer, and substantially the same effect can be obtained by forming only the contact layer in the ridge stripe shape.

(Embodiment 3) In FIG. 6, similarly to (Embodiment 2), a blue light-emitting compound semiconductor formed on an insulating substrate by using a selective growth method to form a ridge stripe shape. 3 shows a laser element. 1 and 3 are denoted by the same reference numerals. Reference numeral 55 denotes a single quantum well structure G
aInN active layer, 101 is an insulating substrate, 102 is GaN
It is a buffer layer. This compound semiconductor laser device has a ridge stripe shape, and furthermore, the protective film is composed of two layers of silicon oxide and aluminum oxide on the surface of the p-type GaAlN upper cladding layer having the ridge stripe shape. This is the same as in Embodiment 2).

Next, a method of manufacturing the compound semiconductor laser device of the third embodiment will be described.

First, fabrication is performed in the same manner as in FIG. 4A of the third embodiment. This step is shown in FIG.

Next, as in the third embodiment, an n-type GaN layer 3, an n-type GaAlN lower cladding layer 4, and a single quantum well structure GaInN active layer 55 (20.degree.
050 ° C. To 5 liters per minute of ammonia per minute 3 × 10 ^-5 mol of TMG, TMA per minute 6 × 10 ^-6 mol and Cp ₂ Mg is flowed min 5 × 10 ^-6 mol, 11-minute treatment By doing so, a 0.43 μm Mg-doped GaAlN upper cladding layer 21a is grown. FIG. 7B is a cross-sectional view after the above steps are completed.

Next, the Mg-doped GaAlN upper cladding
An electron beam evaporation method and photolithography are applied to the surface of the pad layer 21a.
Having an opening 22 with a width of 1 μm by the lithography method
iO _TwoA film 23 is formed. A cross-sectional view after the above process is completed
It is shown in FIG.

Thereafter, S having an opening 22 having a width of 1 μm is formed.
The wafer on which the double heterostructure of the gallium nitride-based compound semiconductor on which the iO ₂ film 23 is formed is
After using a CVD device and replacing the reactor with hydrogen,
The temperature was increased to 1050 ° C. while flowing hydrogen and ammonia, and when the temperature was stabilized at 1050 ° C., TMG was added at 3 × 10 ^-5 mol / min, TMA was added at 6 × 10 ^-6 mol / min, and Cp was added.
₂ Mg per minute 5 × 10 ^{- 6} moles, of ammonia is flowed 5 liters per minute, GaAlN was approximately 0.8μm of Mg doped into the opening 22 of width 1μm by 20 minutes
The upper cladding layer 21b is grown. Since this growth is selectively performed only in the opening 22, the semiconductor layer does not grow on the SiO ₂ film 23 other than the opening 22.

Next, the supply of TMA alone is stopped, and a 0.5 μm Mg-doped GaN contact layer 7 is grown for 10 minutes. As described above, a portion other than the SiO ₂ film 23 is selectively grown to form a ridge stripe shape serving as an optical waveguide. FIG. 7D shows a cross-sectional view after the above steps are completed.

Next, a heat treatment at about 700 ° C. is performed in a nitrogen atmosphere for about 20 minutes to lower the resistance of the Mg-doped GaAlN upper cladding layers 21 a and 21 b and the GaN contact layer 7 to p-type. By this treatment, the hole concentration of both layers is about 1
× 10 ¹⁸ cm ^-3 .

Next, the wafer is formed by using the ordinary photolithography method.
C) Al as a protective film on the entire surface_TwoO_ThreeElectron beam evaporation of film 9
Of the ridge stripe shape
Al _TwoO_ThreeFilm 9 and SiO_TwoStrip film 23 into stripes
Then, an opening 222 is provided. Cross section after completion of the above steps
The figure is shown in FIG.

Next, the wafer in which the opening 222 is formed is introduced into a reactive ion etching apparatus, and in order to form an n-side electrode, the gallium nitride in the opening of the Al ₂ O ₃ film 9 and the SiO ₂ film 23 is formed. The system-based semiconductor layer is etched away to the n-type GaN layer 3 by a normal reactive ion beam etching method. FIG. 7F shows a cross-sectional view after the above steps are completed.

Next, an n-side electrode 11 is formed on the surface of the n-type GaN layer 3 by using a usual photolithography method.

Next, the p-side electrode 10 of the Au / Ni laminated film is entirely formed only on the upper surface of the ridge stripe shape by a vacuum evaporation method using a normal photolithography method.

Next, a mirror surface of the laser resonator is formed. A 500 μm wide SiO ₂ film is used as a mask in a direction orthogonal to the electrode stripes of the Au / Ni laminated film 10 as a mask.
Electron beam evaporation is performed at intervals of 0 μm.

Next, a Si having a stripe of 50 μm
The wafer on which the O ₂ film is formed is introduced into a reactive ion etching apparatus, and a gallium nitride-based semiconductor layer at the opening of the SiO ₂ film is formed up to the AlN buffer layer 2 to form a reflective mirror. Etching is removed by an etching method. Further, the insulating substrate 101 is polished and processed to a thickness of about 100 μm, and the SiO ₂ film used as a mask is removed.

Finally, the laser device is divided into chips by scribing and mounted on a package by an ordinary method to complete a laser device.

When a current was applied to a compound semiconductor laser device having a single quantum well structure active layer manufactured by using the above-mentioned selective growth method, typically, a threshold current of 30 mA was applied at a blue wavelength of 420 nm. Laser oscillation is observed,
As a radiation angle characteristic, a characteristic having an ellipticity of 2 with a vertical divergence angle of 20 ° and a horizontal divergence angle of 10 ° was obtained.
The astigmatic difference was 1 to 5 μm.

In the device manufactured in this embodiment, the oscillation threshold value is 28 mA to 32 mA, and the divergence angle in the horizontal direction is 9.5 ° to 10.5 °. It was shown that the property controllability was more excellent than that of Comparative Example 1.

Also, the compound semiconductor laser device shown in the third embodiment also has a high protective effect since the protective film of the upper cladding layer outside the ridge stripe is formed of two layers of aluminum oxide and silicon oxide. The element life is improved.

In the present embodiment, an element having an active layer having a single quantum well structure has been described. However, a plurality of quantum wells have a multiple quantum well structure.
Three InGaN layers each having a thickness of 0 ° and a barrier layer having a thickness of 30 °
An element structure having a structure in which two GaN layers are alternately stacked. In the case of a multiple quantum well structure,
In consideration of good carrier injection into each quantum well layer and reduction in driving voltage, the number of quantum wells is desirably three or less.

(Embodiment 4) As shown in FIG. 9, a single quantum well structure GaInN fabricated on a conductive substrate by dry etching to form a ridge stripe shape as in (Embodiment 1). 1 shows a blue-emitting compound semiconductor laser device provided with an active layer. 1, 3, and 6 are denoted by the same reference numerals.

The manufacturing method of the compound semiconductor laser device of the fourth embodiment is the same as that of the first embodiment, except that the single quantum well structure GaInN active layer 55 is laminated. It is different from the method of making.

Next, in a reactive ion etching apparatus,
Striped S with etching gas mainly containing chlorine
The same applies to the etching of the Mg-doped GaN layer contact layer 7 and the Mg-doped GaAlN upper cladding layer 6 other than the portion where the iO ₂ film 8 is formed. In this etching step, the Mg-doped GaAlN upper cladding layer 6 is removed. The difference from the first embodiment is that the etching time is adjusted so that the etching is completed while leaving 0.43 μm. Here, the GaN layer contact layer 7 and the Mg-doped GaAs were etched by setting the DC bias to 200 V and the RF power to 300 W as etching conditions.
The etching rate of both the 1N upper cladding layer 6 is 3000 °
/ Min, and the etching was performed for about 3 minutes and 25 seconds. Under the above conditions, the DC bias is ± 50 V and the RF power is ± 50
W, and the variation in the etching rate was about ± 10%.

Next, a heat treatment at about 700 ° C. in a nitrogen atmosphere was performed in the same manner as in the first embodiment.

Further, Au /
The steps of forming the p-side electrode 10 of the Ni laminated film, forming the mirror surface of the laser resonator, and forming the n-side electrode 11 on the entire back surface of the SiC substrate 1 were performed in the same manner as in the first embodiment.

Finally, the laser device is divided into chips by scribing and mounted on a package by a usual method to complete a laser device.

The characteristics of the element manufactured by the manufacturing method by dry etching shown in the fourth embodiment were the same as those of the third embodiment.

In this embodiment, an example of a blue-emitting semiconductor laser device using a GaInN layer as an active layer and GaAlN as a cladding layer has been described. However, the present invention is not limited to this combination. As in the case of the first embodiment, a combination of a GaAlInN-based quaternary compound and a GaN active layer / GaAlN clad layer or a combination capable of laser oscillation may be used.

Further, in the present embodiment, as in the third embodiment, the device provided with the active layer having the single quantum well structure has been described. However, the device provided with the multiple quantum well structure having a plurality of quantum wells exists. In the case of a multiple quantum well structure, a good carrier injection into each quantum well layer,
In consideration of the reduction of the driving voltage, the number of quantum wells is desirably three or less, as in the case of the third embodiment.

[0082]

The gallium nitride-based compound semiconductor laser device as shown in the present embodiment is unlikely to cause a current injection failure or the like due to a variation in etching, unlike a conventional compound semiconductor laser device, and has an oscillation. The threshold was low and the astigmatic difference was small.

The ridge stripe shape of the compound semiconductor laser can be manufactured by either a dry etching method or a selective growth method. In particular, when the selective growth method is used, the controllability of the film thickness of the outer upper cladding layer having the ridge stripe shape is excellent, and the variation of the device is improved. Further, by providing a protective layer on the side surface where the interface between the contact layer and the upper clad layer exists, deterioration of the current injection path can be prevented. Further, by providing two protective films for the upper clad layer, the semiconductor laser device The protection effect is high, and the element life is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a gallium nitride based semiconductor laser device having a ridge stripe shape shown in Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the gallium nitride based semiconductor laser device having the ridge stripe shape shown in the first embodiment.

FIG. 3 is a cross-sectional view of a gallium nitride based semiconductor laser device having a ridge stripe shape shown in a second embodiment.

FIG. 4 is a diagram showing a manufacturing process of the gallium nitride based semiconductor laser device having a ridge stripe shape shown in the second embodiment.

FIG. 5 is a diagram showing the relationship between the thickness of the upper cladding layer outside the ridge stripe shape and the horizontal radiation angle.

FIG. 6 is a cross-sectional view of the gallium nitride based semiconductor laser device having a ridge stripe shape shown in the third embodiment.

FIG. 7 is a diagram illustrating a manufacturing process of the gallium nitride based semiconductor laser device having the ridge stripe shape described in Embodiment 3;

FIG. 8 is a diagram showing the relationship between the thickness of the upper cladding layer outside the ridge stripe shape and the horizontal radiation angle in a device having a single quantum well active layer structure.

FIG. 9 is a cross-sectional view of the gallium nitride based semiconductor laser device having a ridge stripe shape shown in the fourth embodiment.

FIG. 10 is a sectional view of a conventional semiconductor laser device having an electrode stripe structure.

FIG. 11 is a sectional view of a conventional semiconductor laser device having an internal current confinement structure.

[Explanation of symbols]

16H-SiC substrate 101 Insulating substrate 2 AlN buffer layer 102 GaN buffer layer 3 n-type GaN layer 4 n-type GaAlN lower cladding layer 5 InGaN active layer 55 Single quantum well structure InGaN active layer 6 p-type GaAlN upper cladding layer 7 p-type GaN contact layer 8 SiO ₂ film 9 Al ₂ O ₃ protection film 10 p-side electrode 11 n-side electrode 21 a p-type GaAlN upper cladding layer 21 b p-type GaAlN upper cladding layer 22 selectively grown 22 opening 222 opening 23 SiO ₂ membrane

Claims (5)

[Claims] 1. A gallium nitride based semiconductor laser having a substrate, a first conductivity type lower cladding layer, an active layer, a second conductivity type upper cladding layer, and a second conductivity type contact layer in this order. A ridge stripe extending in the resonator direction between the second conductive type upper cladding layer and the second conductive type contact layer; a protective film is formed on a side surface of the ridge stripe; A nitride-based semiconductor laser device, wherein a p-type electrode is formed on the entire upper surface of the ridge stripe. 2. A conductive substrate, a first conductive type lower clad layer, an active layer, a second conductive type upper clad layer,
A gallium nitride based semiconductor laser having a second conductivity type contact layer, wherein the second conductivity type upper cladding layer and the second conductivity type contact layer have a ridge stripe extending in a resonator direction; A nitride semiconductor, wherein a protective film is formed on a side surface of the stripe, and a p-type electrode is formed on the entire upper surface of the ridge stripe, and an n-type electrode is formed on the back surface of the conductive substrate. Laser device. 3. The nitride-based semiconductor laser device according to claim 1, further comprising a protective film on a surface of said ridge stripe-shaped second conductive type upper cladding layer. 4. The first conductivity type lower cladding layer is made of Al.
Consisting of GaN, GaN, or GaAlInN,
The active layer is made of one of InGaN and GaN,
The second conductive type upper cladding layer is made of AlGaN, Ga
4. The nitride-based semiconductor laser device according to claim 1, wherein the nitride-based semiconductor laser device is made of one of N and GaAlInN. 5. The nitride semiconductor laser device according to claim 1, wherein said active layer is a single quantum well layer or a multiple quantum well layer made of InGaN.