JPH0832166A - Semiconductor laser device and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Configuration] The waveguide shape and current injection shape of the semiconductor laser are controlled independently. [Effect] The gain distribution in the stripe can be made uniform, and a new function such as reduction of astigmatism can be added to the semiconductor laser.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a laser beam printer,
The present invention relates to a semiconductor laser used as a light source for an optical disc, a laser processing device, etc.

[0002]

2. Description of the Related Art A conventional semiconductor laser is shown in FIG. 1 (Japanese Journal of Applied Physics Jpn.
As shown in J. of Appl. Phys.), The same mask was used for etching to form a ridge-shaped structure that serves as a laser waveguide and selective crystal growth for current narrowing. Further, as another conventional technique, as shown in FIG. 2, there is a technique in which a mask is side-etched to obtain self-excited oscillation after ridge etching of a conventional semiconductor laser (IEEE J. of Quantum Electronics (IEEE J. of Quantum Electronics)). . Elec.) 25 (1989) 1483
P).

[0003]

In the conventional semiconductor laser described above, the shape of the waveguide and the shape of the current injection have the same or constant constant value over the entire stripe. However, the light intensity distribution inside the semiconductor laser is larger near the end facet, and the amount of current consumption near the end facet is large, so the optical gain in the waveguide becomes non-uniform, and the deterioration of the device progresses in the part where the gain is large. was there. Further, in such a structure, it was not possible to positively utilize the distribution of the refractive index and the gain generated by the current injection to improve the performance and function of the semiconductor laser.

[0004]

In order to solve the above-mentioned problems of the conventional semiconductor laser, the present invention sets the shape of the waveguide of the semiconductor laser and the shape of current injection independently so that the average current density is equal to that of the reflecting surface. Set to be larger than other areas in the vicinity. Furthermore, since the astigmatism of the laser beam can be improved by setting the shape of the waveguide and the shape of the current injection independently, we devised this application example as well.
Such a structure is formed with good reproducibility by removing the unnecessary insulator mask remaining under the resist by side etching when the mask for stripe formation is formed and leaving only the resist mask and the insulator mask embedded in the resist mask. I was able to.

[0005]

According to the consumption of carriers by the light inside the semiconductor laser, the current injection amount is optimally set for each stripe position to keep the electron and hole densities in the active layer during laser oscillation constant. The local deterioration of crystal was prevented from proceeding rapidly. It was also possible to obtain a low-aberration semiconductor laser by setting the refractive index distribution near the laser emission end face so as to eliminate astigmatism, which was a problem with conventional semiconductor lasers. Furthermore, by narrowing the current injection width at the center of the stripe of such a semiconductor laser, self-excited oscillation is generated, and it becomes possible to realize a semiconductor laser with low noise and low aberration.

[0006]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described with reference to the drawings. In this structure, as shown in FIGS.
On the -GaAs substrate 101, n-Al _0.5 Ga _0.5 As cladding layer 102, multiple quantum well active layer 103, p-Al _0.5 Ga _0.5 As
The clad layer 104 and the p-GaAs contact layer 105 were sequentially grown. The multiple quantum well active layer 103 is shown in FIG.
GaAs well layer (three layers) 106 and Al _0.3 G
a _0.7 As barrier layers (4 layers) 107 are alternately laminated.

Next, by using a thermal CVD method and an electron beam lithographic technique for this structure, a stripe-shaped resist film 108 having a width of 7 μm and a 5 μm square SiO ₂ film 109 embedded in the resist film 108 are formed. A mask as shown in FIG. 3 is formed. The SiO ₂ film 109 is intermittently formed along the stripes, and the interval is 10 μm in the region from the element center to the rear end face, and is 1/4 from the element center.
5 μm in the area up to and 2 in the area 1/4 in front of the element
μm.

Using the resist film as a mask, p-Al _0.5 G
After etching a part of the a _0.5 As clad layer 104, the resist is removed, and the n-GaAs block layer 110 is SiO 2 by metal organic chemical vapor deposition using the SiO ₂ film as a mask.
₂ It grew selectively in the region without film. In order to reduce the series resistance of the device, the p-GaAs cap layer 111 was formed after removing the SiO ₂ film.

FIG. 4 (a) shows a wafer cross section in the region with SiO ₂ at this stage, and FIG. 4 (b) shows a wafer cross section in the region without SiO ₂ .

Electrode 1 containing Au as a main component on the surface of the wafer
12 to form G by mechanical polishing and chemical etching.
The aAs substrate was etched to about 100 μm, and the electrode 112 containing Au as a main component was also formed on the GaAs substrate side. Such a semiconductor wafer was cleaved into bars at intervals of about 600 μm.

According to this structure, current injection corresponding to the amount of charged particles consumed in each region of the waveguide is performed, so that the density of charged particles is kept constant, and regions where the deterioration progressing speed is high are not formed. A semiconductor laser with high reliability can be obtained. The semiconductor laser of the present invention showed stable operation for 100,000 hours or more at an optical output of 20 mW.

(Second Embodiment) A second embodiment of the present invention will be described with reference to the drawings. In this structure, as shown in FIGS. 5A and 5B, n-Zn _0.9 Mg _0.1 S is first formed on the n-GaAs substrate 101.
_0.14 Se _0.86 clad layer 201, multiple quantum well active layer 2
02, p-Zn _0.9 Mg _0.1 S _0.14 Se _0.86 clad layer 203,
The p-ZnSe contact layer 204 was sequentially crystal-grown. The multiple quantum well active layer 202 is formed by alternately stacking a CdZnSe well layer (3 layers) 205 and a ZnS _0.07 Se _0.93 barrier layer (4 layers) 206 as shown in FIG. 5C.

Next, a resist film 1 having a stripe shape with a width of 7 μm is formed on this structure by using a thermal CVD method and a lithographic technique.
08 and a mask as shown in FIG. 3 which is composed of a 5 μm square SiO ₂ film 109 embedded in the resist film is formed. The SiO ₂ film is formed intermittently along the stripes, and the spacing is 10 μm in the region from the rear end face to the element center, 5 μm in the region from the element center to the quarter, and 1/4 in the front of the element. The area is 2 μm.

Using the resist film as a mask, p-Zn _0.9 Mg _0.1
After etching a part of the S _0.14 Se _0.86 clad layer 203, the resist was removed and the n-Zn _0.54 Cd _0.46 S block layer 2 was formed by metal organic chemical vapor deposition using the SiO ₂ film as a mask.
07 was selectively grown in a region having no SiO ₂ film. In order to reduce the series resistance of the device, after removing the SiO ₂ film, p-Zn
An S _0.6 Te _0.4 cap layer 208 was formed.

FIG. 5 (a) shows a wafer cross section in this region in which SiO ₂ exists, and FIG. 5 (b) shows a wafer cross section in the region without SiO ₂ described above.

Next, an electrode 112 containing Au as a main component is formed on the surface of the wafer, and the GaAs substrate is etched to about 100 μm by mechanical polishing and chemical etching.
The electrode 112 containing Au as a main component was also formed on the As substrate side. Such a semiconductor wafer was cleaved in a bar shape at intervals of about 900 μm.

According to this structure, since current is injected corresponding to the amount of charged particles consumed in each region of the waveguide, the density of charged particles is kept constant and a region where the deterioration progressing speed is high is formed. Therefore, a highly reliable semiconductor laser can be obtained. The semiconductor laser of the present invention showed stable operation for 10,000 hours or more at an optical output of 10 mW.

(Embodiment 3) A third embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 7A and 7B, in this structure, first, n- (Al _0.7 Ga) is formed on the n-GaAs substrate 101.
_0.3 ) _0.5 In _0.5 P clad layer 301, multiple quantum well active layer 302, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 30
Crystal growth of the 3, p-GaAs contact layer 304 was sequentially performed. As shown in FIG. 7C, the multi-quantum well active layer 302 is composed of Ga _0.6 In _0.4 P well layers (three layers) 305 and (Al).
_0.7 Ga _0.3 ) _0.5 In _0.5 P Barrier layers (four layers) 306 are alternately laminated.

Next, by using a thermal CVD method and a lithographic technique for this structure, a stripe-shaped resist film 1 having a width of 7 μm is formed.
08 and the SiO ₂ film 30 embedded in this resist film
A mask constituted by 7 is formed as shown in FIG. S
The iO ₂ film has a thickness of about 3 μm in the region of about 30 μm near the end face of the device.
2 are formed in parallel with each other, and only one stripe of about 3 μm is formed in the other regions.

Using the resist film as a mask, p- (Al _0.7 Ga
_0.3 ) _0.5 In _0.5 P After partially etching the clad layer 303, the resist is removed and the n-GaAs block layer 110 is formed by metalorganic vapor phase epitaxy using the SiO ₂ film as a mask.
Were selectively grown in the region without the SiO ₂ film. To reduce the series resistance of the device, after removing the SiO ₂ film, p-GaAs
The cap layer 111 was formed. FIG. 7A shows the central portion of the device at this stage, and FIG. 7B shows the wafer cross section in the end region of the device. An electrode 112 containing Au as a main component is formed on the surface of the wafer, and GaAs is formed by mechanical polishing and chemical etching.
The substrate was etched to about 100 μm, and an electrode 112 containing Au as a main component was also formed on the GaAs substrate side. Such a semiconductor wafer was cleaved into bars at intervals of about 600 μm.

According to this structure, the distribution of the refractive index due to the current injection in the vicinity of the light emitting end face becomes larger toward the center of the stripe. In conventional semiconductor lasers, the decrease in the refractive index at the center of the stripe due to current injection caused astigmatism, but this structure creates a refractive index distribution that cancels out such a phenomenon by current injection. Therefore, astigmatism can be prevented from occurring. The astigmatism of the semiconductor laser of the present invention is 3 μm in the range of light output of 1 mW to 100 mW.
It was within.

(Embodiment 4) A fourth embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 9A and 9B, in this structure, first, on the n-GaAs substrate 101, the n-Al _0.5 Ga _0.5 As clad layer 102, the multiple quantum well active layer 103, and the p-Al are formed.
_{The 0.5} Ga _0.5 As clad layer 104 and the p-GaAs contact layer 105 were sequentially crystal-grown. As shown in FIG. 9C, the multiple quantum well active layer 103 includes a GaAs well layer (three layers) 106 and an Al _0.3 Ga _0.7 As barrier layer (four layers) 107.
Are alternately laminated.

Next, a stripe-shaped resist film 108 having a width of 7 μm and a SiO ₂ film embedded in this resist film are formed on this structure by using a thermal CVD method and a photolithographic technique.
A mask as shown in FIG. 8 constituted by 401 is formed.
As shown in FIG. 10, the mask having such a shape is made of Si.
SiO ₂ mask 501 in which holes 502 corresponding to a desired resist mask shape are provided around the O ₂ stripe pattern.
After the formation of the film, it can be easily realized by covering it with a striped resist film 108 and removing the unnecessary SiO ₂ film 503 by side etching using a hydrofluoric acid-based etching solution.

The SiO ₂ film has a width of about 7 μm in the region of about 30 μm near the element end face, and has a width of about 3 μm in other regions. P-Al as a resist film mask
After etching a part of the _0.5 Ga _0.5 As clad layer 104, the resist is removed, and the n-GaAs block layer 108 is selectively formed in a region having no SiO ₂ film by metal organic chemical vapor deposition using the SiO ₂ film as a mask. grown. In order to reduce the series resistance of the device, after removing the SiO ₂ film, p-GaA
The s cap layer 109 was formed.

[0025] 9 (a) is a region 9 with a SiO ₂ at this stage (b) denotes a wafer cross-section of the SiO ₂ has no area. An electrode 112 containing Au as a main component is formed on the surface of the wafer, and the GaAs substrate is etched to about 100 μm by mechanical polishing and chemical etching.
The electrode 112 containing Au as a main component was also formed on the s substrate side. Such a semiconductor wafer was cleaved into bars at intervals of about 600 μm to obtain semiconductor laser chips.

According to this structure, current is injected corresponding to the amount of charged particles consumed in each region of the waveguide, so that the density of charged particles is kept constant, and a region where the deterioration progressing speed is high is not formed. A semiconductor laser with high reliability can be obtained. Moreover, although self-excited oscillation occurs in the central region of the device, the return light noise of the semiconductor laser can be reduced. The problem of astigmatism, which was a problem, can be solved.

[0027]

According to the present invention, the uniformity of the density of charged particles in the active layer of a semiconductor laser can be improved, so that a region where deterioration progresses quickly is not formed.

Further, the function of correcting astigmatism of the semiconductor laser which deflects the emission direction of the laser beam by utilizing the refractive index distribution generated inside the stripe of the semiconductor laser is improved.

[Brief description of drawings]

FIG. 1 is a perspective view of a conventional semiconductor laser structure.

FIG. 2 is a perspective view of another conventional semiconductor laser structure.

FIG. 3 is a plan view of the mask structure of the semiconductor laser according to the first embodiment of the present invention.

FIG. 4 is a sectional view of the semiconductor laser according to the first embodiment of the present invention.

FIG. 5 is a sectional view of a semiconductor laser according to a second embodiment of the present invention.

FIG. 6 is a plan view of a mask structure of a semiconductor laser according to a third embodiment of the present invention.

FIG. 7 is a sectional view of a semiconductor laser according to a third embodiment of the present invention.

FIG. 8 is a plan view of a mask structure of a semiconductor laser according to a fifth embodiment of the present invention.

FIG. 9 is a sectional view of a semiconductor laser according to a fifth embodiment of the present invention.

FIG. 10 is an explanatory diagram of a mask forming method according to a fifth embodiment of the present invention.

[Explanation of symbols]

101 ... n-GaAs substrate, 102 ... n-Al _0.5 Ga
_0.5 As clad layer, 103 ... Multiple quantum well active layer, 1
04 ... p-Al _0.5 Ga _0.5 As clad layer, 105 ... p
-GaAs contact layer, 106 ... GaAs well layer,
107 ... Al _0.3 Ga _0.7 As barrier layer, 110 ... n-GaAs
Block layer, 111 ... p-GaAs cap layer, 112 ... A
u electrode.

Claims (5)

[Claims] 1. A semiconductor laminated structure that generates an optical gain when energized, a waveguide structure for confining light in a plane of the semiconductor layer, and a current constriction structure for narrowing a current inside the waveguide structure, In a semiconductor laser that constitutes an optical resonator by reflecting light from at least a pair of reflecting surfaces to the waveguide structure, the shape of the waveguide structure and the shape of current injection are set independently. Semiconductor laser. 2. The semiconductor laser according to claim 1, wherein the shape of the current injection region is set so that the average current density is larger in the vicinity of the reflection surface than in other regions. 3. The semiconductor laser according to claim 1, wherein the current injection region is set so as to correct the bend of the wavefront of the laser light near the end face of the semiconductor laser. 4. The semiconductor laser according to claim 3, wherein the width of the current injection region is set so as to cause longitudinal multimode oscillation or self-excited oscillation in a region other than the vicinity of the reflection surface. 5. The method for producing a semiconductor laser according to claim 1, further comprising a step of removing an unnecessary insulating material mask under the resist by side etching.