JP3038186B2 - Method for manufacturing semiconductor laser device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a light source or the like in the field of information and video such as optical communication and optical disks, and is used to manufacture a high-output and stable semiconductor laser device. It is about the method. 2. Description of the Related Art Semiconductor lasers have been widely used as light sources for optical disk devices and the like. Light output as high as 40 mW is required. Currently, semiconductor lasers having relatively high output are put to practical use, but it has been reported that the reliability of semiconductor lasers is inversely proportional to the fourth power of optical output when compared with devices having the same structure. it is conceivable that. It is well known that one of the causes of deterioration of a high power semiconductor laser is deterioration of a light emitting end face. FIG.
FIG. 1 shows an example of a structure diagram of a conventional semiconductor laser. This structure is called VSIS (V-channeled Substr
ate Inner Stripe) This is called a laser. In this conventional structure, the p-GaAs substrate 1
After an n-GaAs current blocking layer 12 for interrupting current is deposited on the
A mold groove is formed. A p-GaAlAs cladding layer 13, a GaAs or GaAlAs active layer 14, an n-G
aAlAs cladding layer 15, n-GaAs cap layer 1
6 are sequentially deposited. In this case, the current for laser oscillation is confined by the n-GaAs layer 12 and has a width W _1.
Flows only in the channel section of Although the active layer 14 is formed flat, the effective refractive index is lowered by light absorption into the n-GaAs layer 12 on both sides of the channel, so that an optical waveguide is formed, and stable fundamental transverse mode oscillation is obtained. . That is,
It has an element of a loss guiding mechanism. The above-mentioned VSIS laser has a drawback that stable fundamental transverse mode oscillation is obtained and the reliability is high at a low optical output level, but the reliability is greatly reduced at a high output level, and the laser cannot be used for a long time. Was. When the cause of the above-mentioned deterioration is examined in detail, the deterioration of the element is caused by the deterioration of the V-groove shoulder at the end face, and the n-GaAs layer 12 at the V-groove shoulder is deteriorated. It has been revealed that heat generation due to light absorption of this is a major cause. That is, in a conventional semiconductor laser device having an element of the loss guiding mechanism, the temperature of the laser end face rises due to light absorption on both sides of the channel near the end face of the resonator. The rise causes deterioration of the end face, and reduces reliability in a high output state. [0009] The present invention relates to a substrate or a substrate.
A stripe-shaped groove is formed in the semiconductor layer on the board, and
Crystal growth by liquid phase growth method, semiconductor laser device
When manufacturing, the stripe-shaped groove, the end face of the resonator
More broadly, the steps of narrower formed in the cavity center portion, before
Fill the grooves to form a cladding layer with a substantially flat top surface
Process and a flat plate having a uniform thickness on the cladding layer.
It includes a step of forming an active layer, wherein the stripe
Regardless of the width of the groove, above the cladding layer formed immediately above
The surface is substantially flat . According to the present invention, the effect of the present invention can be more preferably obtained by forming the stripe-shaped groove wider in a region within 30 μm from the end face. In the semiconductor device manufactured by the manufacturing method of the present invention described above, the absorption of light at the end face is suppressed by forming a channel width wider than at the center near at least one laser resonator end face. , Is configured to suppress heat generation as much as possible. Therefore, a main object of the present invention is to provide a semiconductor laser device that suppresses deterioration at the semiconductor laser end face and operates stably even in a high output state. In the semiconductor laser device manufactured by the manufacturing method according to the present invention, the temperature rise at the end face portion is reduced by changing the structure of the end face portion of the laser from that of the conventional one, so that the deterioration is suppressed and the high output state is suppressed. However, stable and stable fundamental transverse mode oscillation can be obtained with high reliability. FIG. 1 is an exploded perspective view schematically showing a semiconductor laser device according to an embodiment of the present invention.
It is composed of end portions A and C and a center portion B arranged along the resonance direction. FIG. 2 schematically shows a channel forming state of the present embodiment. Hereinafter, the manufacturing procedure of this example will be described in detail. First, an n-GaAs current blocking layer 12 is deposited to a thickness of about 0.7 μm on a p-GaAs substrate 11 by a liquid phase epitaxial growth method, and then the vicinity of an end face as shown in FIG. To form a groove having a width W ₂ = 10 μm and a width W ₁ = 4 μm and a depth ₁ μm at the center of the resonator. n-Ga
As a growth method of the As current blocking layer 12, a vapor phase growth method or the like may be used. Thereafter, a p-Al _0.42 Ga _0.58 As clad layer 13 as shown in FIG. 1 is formed to a thickness of 0.15 μm on the outer side of the groove by a liquid phase epitaxial growth method.
The l _{0. 14} Ga _0.86 As active layer 14 to 0.08μm thickness, further n-Al _0.42 Ga _0.58 As clad layer 15 0.8
The thickness of the n-GaAs-contact layer 16 is 1.5 μm
Each is grown thick. In the liquid phase epitaxial growth method, the growth is performed so as to flatten the depressed portion. Therefore, after the p-Al _0.42 Ga _0.58 As clad layer 13 is grown, the growth surface is flat and Al _0.14 Ga _0.86 to be subsequently grown.
The As active layer 14 can also be grown to a flat and uniform thickness over the entire surface. After that, a resistive full surface electrode is provided on both surfaces of the wafer, an alloying process is performed, and cleavage is performed in a region having a wide stripe width to form a resonator. In this embodiment, the length of the laser resonator is 250 μm, and the region where the stripe width is wide is 10 μm on each end face. Therefore, n-Ga on both end surfaces of the semiconductor laser is
There is no light absorption by the As current blocking layer 12, the temperature rise of the end face is suppressed, high reliability is exhibited, and the coating on the output side end face 4% and the reflectivity on the back side 97% is applied. It showed no deterioration characteristics. In this embodiment, the length of the wide channel portion is set to 10 μm at both ends. If the length is within 30 μm, light guided at the central portion of the resonator is completely removed by the wide channel portion. Does not undergo mode deformation and exhibits stable transverse mode characteristics. In addition, the effect is exhibited even when the wide channel portion is formed only on the emission side end face portion. FIG. 3 is an exploded perspective view schematically showing a semiconductor laser device according to another embodiment of the present invention. This embodiment is an embodiment in which the channel width near the end face of the resonator is extended to the side wall surface of the substrate. FIG. 4 shows a manufacturing procedure of this embodiment.
It is explained along. First, n is formed on the p-GaAs substrate 11.
A GaAs current blocking layer 12 is deposited to a thickness of about 0.7 μm as shown in FIG. Thereafter, an SiO ₂ film 31 having a thickness of 0.3 μm is formed by a sputtering method, and the length of a portion serving as both end faces of the laser resonator is set to 1 using the mask as a mask.
A groove having a depth of 0.8 μm is formed over 0 μm. This is the state shown in FIG. Then, using the SiO ₂ film as a mask as it is, an organic metal thermal decomposition method (MOC)
Using a VD method, a p-Al _0.42 Ga _0.58 As layer 32 is deposited to a thickness of 0.8 μm, and an undoped GaAs etch-back layer 33 is deposited to a thickness of 0.05 μm to facilitate subsequent growth (FIG. c)). In this state, n-GaAs
The surface heights of the current blocking layer 12 and the p-Al _0.42 Ga _0.58 As layer 32 are uniform and coincide with each other. Next, SiO ₂
After the film 31 is removed by etching, FIG width V-shaped grooves reaching the p-GaAs substrate 11 as shown in (e) W ₁
= 4 μm and depth 1 μm. Then, the conventional VS
P using liquid phase growth in the same manner as the IS laser growth method
-Al _0.42 Ga _0.58 As clad layer 13 is 0.15 μm thick outside the groove, p or n-Al _0.14 Ga _0.86 As active layer 14 is 0.08 μm thick, n-Al _0.42 Ga _0.58 A
The s cladding layer 15 is grown to a thickness of 0.8 μm, and the n-GaAs contact layer 16 is grown to a thickness of 1.5 μm. In the liquid phase epitaxial growth method, since the growth is performed so as to flatten the depression, p-Al
After the growth of the _0.42 Ga _0.58 As cladding layer 13, the growth surface is flat, and the subsequently grown Al _0.14 Ga _0.86 As active layer 14 can also be grown flat and uniform over the entire surface. The undoped GaAs etch-back layer 33 effectively prevents the oxidation of the p-Al _0.42 Ga _0.58 As layer 32 and disappears by the etch-back during liquid phase growth. This means that the film was uniformly formed to a thickness of 95 μm, and there was no light absorption at this portion. Then, apply resistive full surface electrodes on both sides of the wafer,
After performing the alloying treatment, the portion where the n-GaAs current blocking layer 12 does not exist is cleaved to form a resonator. This laser does not absorb light at both end faces, suppresses temperature rise at the end faces, exhibits high reliability, and exhibits an emission end face 4.
When a coating having a reflectance of 97% on the back surface side was applied, almost no deterioration was exhibited even in a high output state of 80 mW. In this embodiment, the length of the end face where the n-GaAs current blocking layer 12 is not present is set to 10 μm at both ends of the resonator. If this length is within 30 μm, the waveguide is guided at the center of the resonator. The emitted light does not undergo mode deformation even at the end face, and exhibits stable transverse mode characteristics. Further, the effect can be exerted even when the portion where the n-GaAs current blocking layer 12 does not exist is formed only on the end face on the emission side. In the above embodiment, a case where the present invention is applied to a VSIS type semiconductor laser is shown. Next, a case where the present invention is applied to another structure will be described. One of the other structures is a CPS laser (Transverse Mode Stabilized Al _x Ga _1-x As Injection
Lasers with Channeled-Planar Structure; IEEE JOURNA
L OF QUANTUM ELECTRONICS, vol, QE-14, No.2, February19
87, p89). FIG. 5 shows an embodiment in which the present invention is applied to a CSP laser. In this embodiment, a channel is formed n-GaAs substrate 11, but this time, so that the channel width W ₂ of the end face than the channel width W ₁ of the central portion is increased. Thereafter, the n-Al _x Ga _{1 -x} As clad layer 42,
Creating a current path by forming a GaAs active layer _{43, p-Al x Ga 1} -x As cladding layer 44, the diffusion region 48 of the Zn after the formation of the n-GaAs layer 45. Also in this case, light is absorbed by the n-GaAs substrate outside the channel and heat is generated at the shoulder of the channel. However, by increasing the channel width at the end face, the heat is reduced and reliability is improved. Also in this case, the substrate may be etched to the same depth as the channel over the entire surface at the end face portion, and the effect is exhibited even if such a structure is formed only on one end face or on both sides. In the above embodiment, a semiconductor laser having a double hetero junction structure has been described.
For example, LOC (Large Optical Cavity) structure, SCH
(Separate Confinement Heterostructure) Structure The present invention is also applicable to a case where another structure such as a quantum well structure is used. For example, FIG. 6 shows an example in which the present invention is applied to an LOC structure, in which an optical waveguide layer 18 is laminated adjacent to an active layer 14, but the same effect as in the above embodiment can be recognized.
FIG. 7 shows one example of the case where the present invention is applied to the quantum well structure.
GRIN-SCH-SQW (Graded Index
-Separate Confinement Hetetostructure-Single Quant
FIG. 3 is a configuration diagram showing a um well) structure, and the same effects as in the above embodiment are observed. FIG. 8 shows the distribution of the mixed crystal ratio of the active layer in the embodiment of FIG. According to the present invention, by increasing the channel width of the end face, it is possible to prevent a temperature rise due to light absorption at the emission end face, and to have a high reliability even in a high output state. A device can be manufactured. Further, according to the manufacturing method of the present invention, it is possible to easily fill even the stripe-shaped through grooves having different widths.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded configuration diagram of a semiconductor laser device showing one embodiment of the present invention. FIG. 2 is a structural perspective view after a channel is formed. FIG. 3 is an exploded configuration diagram of a semiconductor laser device according to another embodiment of the present invention. FIG. 4 is a cross-sectional view schematically showing a manufacturing process of the element. FIG. 5 is an exploded configuration diagram of a semiconductor laser device showing another embodiment of the present invention. FIG. 6 is an exploded configuration diagram of a semiconductor laser device showing another embodiment of the present invention. FIG. 7 is an exploded configuration diagram of a semiconductor laser device showing another embodiment of the present invention. FIG. 8 is an explanatory diagram schematically showing a structure of an active layer of the semiconductor laser device shown in FIG. 7; FIG. 9 is a structural view of a conventional semiconductor laser device. DESCRIPTION OF SYMBOLS 11 p-GaAs substrate 12 n-GaAs current blocking layer 13 p-Al _0.42 Ga _0.58 As clad layer 14 p or n-Al _0.14 Ga _0.86 As active layer 15 n-Al _0.42 Ga _0.58 As clad layer 16 n-GaAs contact layer 17 p-Al _0.4 Ga _0.6 As clad layer 18 p-Al _0.3 Ga _0.7 As guide layer 19 n-Al _0.7 Ga _0.3 As clad layers 21 and 22 Resistive electrode 31 SiO ₂ film 32 p-Al _0.42 Ga _0.58 As layer 33 Undoped GaAs etch-back layer 41 n-GaAs substrate 42 n-Al _x Ga _1-x As cladding layer 43 GaAs active layer 44 p-Al _x Ga _1-x As cladding layer 45 n-GaAs layer 46; 47 resistive electrode 48 Zn diffusion region 51 p-Al _0.7 Ga _0.3 As cladding layer 52 GRIN-SCH-SQW active Layer 53 n-Al _0.7 Ga _0.3 As cladding layer

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yasushi Morimoto               22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture               Sharp Corporation (72) Inventor Shinji Kaneiwa               22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture               Sharp Corporation (72) Inventor Masahiro Yamaguchi               22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture               Sharp Corporation                (56) References JP-A-63-293989 (JP, A)                 JP-A-59-152686 (JP, A)                 IEICE Technical Report (1982) E               D82-37, p. 9-15                 Appl. Phys. Lett. 50               [5] (1987) p. 233-235

Claims (1)

(57) [Claims] Stripe-shaped grooves in the substrate or semiconductor layer on the substrate
And then grow crystals on it by liquid phase epitaxy.
When manufacturing a semiconductor laser device, the stripe-shaped groove is made wider at the cavity end face,
A step of narrower formed in vessel center portion to form a substantially flat cladding layer upper surface embed the groove
And forming a flat active layer having a uniform thickness on the cladding layer.
A forming and, regardless of the width of the stripe-shaped groove, it is formed immediately above
The method of manufacturing a semiconductor laser device the upper surface of the cladding layer is characterized by comprising a Ryakutaira sputum to be. 2. The groove in the form of a stripe is within 30 μm from the end face.
In the area, the width is formed wider
Made in the semiconductor laser device according to claim 1, wherein
Construction method.