JP3075512B2 - 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 images such as optical communication and optical disks. It is about structure. 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. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a flat plate-like active layer having a uniform thickness and laminated above a substrate; close to the active layer includes a substrate formed with grooves of the light-absorbing layer or a stripe-shaped recess having a stripe-shaped through groove, the at least one of the light absorbing layer or the in the resonator near the end faces The groove width of the through groove of the light absorbing layer or the groove of the concave portion of the substrate is set such that light absorption by the substrate is smaller than light absorption by the light absorbing layer or the substrate at the resonator center. The resonator is characterized in that it is enlarged near at least one end face of the resonator from the center of the resonator. Further, another invention of the present application is directed to a flat-plate-shaped active layer having a uniform thickness and a light-absorbing layer or a stripe-shaped through-groove in the vicinity of the active layer. has between substrate formed with grooves of the recess, the at least one of the light absorbing layer or the absorption of light by the substrate in the resonator facet vicinity, the optical absorption layer or the substrate in the cavity center portion As a result, the groove width of the through groove of the light absorbing layer or the groove of the concave portion of the substrate is larger than the central portion of the resonator in the vicinity of at least one end face of the resonator, A region where the groove width of the through groove of the light absorbing layer or the groove of the concave portion is enlarged near at least one end surface of the resonator is a region where the width is substantially constant near the end surface of the resonator, and a center of the resonator. Having a gradually expanding area leading to the part It is an feature. Further, the light output of the semiconductor laser device is 80 mW.
It is characterized by the following. In the semiconductor device of the present invention, the channel width is formed wider at least in the vicinity of the end face of the laser resonator than at the center, thereby suppressing light absorption at the end face and generating heat as much as possible. Is configured to be suppressed. 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 according to the present invention, by changing the structure of the end face of the cavity of the laser from that of the prior art, the temperature rise at the end face is reduced, so that deterioration is suppressed and high reliability is maintained even in a high output state. A stable and fundamental transverse mode oscillation can be obtained. 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 embodiment 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, as shown in FIG. 1 by ordinary photolithography and etching. Width W ₂ = 10 μm in the vicinity of a simple end face and width W ₁ = in the center of the resonator
A groove of 4 μm and a depth of 1 μm is formed. As a method for growing the n-GaAs 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 cladding layer 13 as shown in FIG. 1 is formed to a thickness of 0.15 μm on the outside of the groove by a liquid phase epitaxial growth method.
l _0.14 Ga _0.86 As active layer 14 has a thickness of 0.08 μm, and n-Al _0.42 Ga _0.58 As cladding layer 15 has a thickness of 0.8 μm.
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, and an alloying process is performed. After that, the wafer is cleaved 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
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, the light guided at the center 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 a schematic exploded perspective view of 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-Ga is placed on a p-GaAs substrate 11.
As 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 the both end surfaces of the laser resonator is reduced to 10 μm using the mask as a mask.
A groove having a depth of 0.8 μm is formed over m. This is the state shown in FIG. After that, using the SiO ₂ film as a mask as it is, an organic metal thermal decomposition method (MOCVD)
Method) to form a p-Al _0.42 Ga _0.58 As layer 32 of 0.8
An undoped GaAs etch-back layer 33 is deposited to a thickness of 0.05 μm for smoothing later growth (FIG. 4C). In this state, the surface heights of the n-GaAs current blocking layer 12 and the p-Al _0.42 Ga _0.58 As layer 32 are uniform and coincide with each other. Next, the SiO ₂ film 31
After removal by etching, FIG width V-shaped grooves reaching the p-GaAs substrate 11 as shown in (e) W ₁ = 4μ
m and a depth of 1 μm. After that, p-Al is formed using liquid phase growth in the same manner as the conventional VSIS laser growth method.
_0.42 Ga _0.58 As clad layer 13 is formed on the outer side of the groove by 0.15
p or n-Al _0.14 Ga _0.86 As active layer 14
Is grown to a thickness of 0.08 μm, the n-Al _0.42 Ga _0.58 As 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, the growth is performed so as to flatten the depressed portion. Therefore, after the growth of the p-Al _0.42 Ga _0.58 As clad layer 13, the growth surface is flat, and the subsequently grown Al _0.14 Ga _0.86 The 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 the 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. Also,
The effect is exhibited 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, the semiconductor laser having the 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 a case where the present invention is applied to a LOC structure, and an optical waveguide layer 18 is laminated adjacent to the 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 at the end face, it is possible to prevent a temperature rise due to light absorption at the emission end face, and to achieve high reliability even in a high output state where the active layer is larger than the groove width. have a gender, and, variations in device characteristics small
And the active layer is larger than the channel width.
Since the region is flat, deterioration due to heat generation in the active layer is suppressed.
A controlled semiconductor laser device is obtained.

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)                 Appl. Phys. Lett. 50               [5] (1987) p.233-235

Claims (1)

(57) [Claims] Forming a plate-shaped active layer having a uniform thickness and a light-absorbing layer having a stripe-shaped through groove or a groove having a stripe-shaped recess close to the active layer.
And the substrate has a light absorption by the light-absorbing layer or the substrate in at least one of the resonator end face neighborhood is reduced from light absorption by the light-absorbing layer or the substrate in the cavity center portion The groove width of the through groove of the light absorbing layer or the groove of the concave portion of the substrate is near at least one end face of the resonator,
A semiconductor laser device which is enlarged from a central portion of a resonator. 2. Forming a plate-shaped active layer having a uniform thickness and a light-absorbing layer having a stripe-shaped through groove or a groove having a stripe-shaped recess close to the active layer.
And the substrate has a light absorption by the light-absorbing layer or the substrate in at least one of the resonator end face neighborhood is reduced from light absorption by the light-absorbing layer or the substrate in the cavity center portion The groove width of the through groove of the light absorbing layer or the groove of the concave portion of the substrate is near at least one end face of the resonator,
A region that is enlarged from the central portion of the resonator and has a groove width of the through groove of the light absorbing layer or the groove width of the concave portion that is enlarged near at least one end face of the resonator has a width near the resonator end face. A semiconductor laser device comprising: a substantially constant region; and a gradually enlarged region connected to a central portion of the resonator. 3. 3. The semiconductor laser device according to claim 1, wherein an optical output of the semiconductor laser device is 80 mW or less.