JPH0135488Y2 - - Google Patents

Description

[Detailed explanation of the idea] (b) Industrial application fields The present invention relates to semiconductor lasers.

(b) Prior art A conventional semiconductor laser is, for example, an n-type GaAs (gallium arsenide) substrate with an n-type Ga _1-XAlXAS (0<X<1)
N-type, clad layer, non-doped
Active layer consisting of Ga _1-YAlYAS (0≦Y<X), P type
After sequentially stacking P-type clad layers made of Ga _1-XAlXAS , a scribe line is formed on the back surface of the substrate as disclosed in Japanese Patent Laid-Open No. 57-66688, and the layers are separated along the scribe line. Separated into chips. Therefore, the four side faces of such a chip, including the resonator end faces, are flat surfaces with few irregularities.

However, if the four sides are flat like this, when the chip is clamped with tweezers, the impurities that have adhered to the tweezers will adhere to the side surfaces of the chip, and then these impurities will naturally form in each of the layers. This poses a problem in that it can diffuse into the layers and short-circuit the junctions between the layers.

In addition, since semiconductor chips generally bond the surface of the P-type cladding layer onto a heat sink,
As mentioned above, if the side surfaces are flat, there is a problem in that short circuits occur due to creeping of the solder material.

(c) Purpose of the invention This invention was made in view of the above problems.
It is an object of the present invention to provide a semiconductor laser which can suppress short circuits caused by the impurity diffusion and/or solder material creep-up as much as possible.

(d) Structure of the invention The structural features of the invention include a first semiconductor layer, a second semiconductor layer sandwiching the semiconductor layer, and a second and third semiconductor layer having a larger bandgap and a smaller optical refractive index than the first semiconductor layer. The present invention includes an oscillation layer having a semiconductor layer, and a side surface of the oscillation layer other than a resonator end face is formed with unevenness in the stacking direction of the respective layers.

(E) Embodiment Figure 1 shows an embodiment of the present invention, in which 1 is an n-type GaAs substrate with one principal surface of the (100) plane, and 2 is an oscillation layer laminated on one principal surface of the substrate. , the oscillation layer is formed by sequentially laminating a first cladding layer 3, an active layer 4, and a second cladding layer 5. The first cladding layer 3 is of n-type
It consists of Ga _1-XAlXAS (0<X<1), and the active layer 4 consists of non-doped n-type Ga _1-YAlYAS (0≦Y<X),
Further, the second cladding layer 5 is made of P-type Ga _1-XAlXAS . 6 is a cap layer formed on the oscillation layer 2, and the cap layer is made of P-type GaAs.
7 is SiO ₂ formed on the cap layer 6;
This is an insulating layer made of Si ₃ N ₄ or the like, and a portion of the insulating layer is removed in a stripe pattern in the direction perpendicular to the plane of the paper, that is, in the (110) direction. A first electrode 8 is formed on the insulating layer 7 and the cap layer 6, and is in ohmic contact with the cap layer 6. Reference numeral 9 denotes a second electrode, which is formed on the back surface of the substrate 1 and is in ohmic contact with the substrate.

In such a semiconductor laser, two planes perpendicular to the direction perpendicular to the plane of the paper act as flat cleavage planes and act as end faces of the resonator, and side surfaces 10a and 1 extending in the direction perpendicular to the plane of the paper act as flat cleavage planes.
0b has unevenness formed in the lamination direction of each layer. In this embodiment, such unevenness is the side surface 10a,
The active layer 10b is formed by making the side surface of the active layer 4 go inside the side surfaces of the first and second cladding layers 3 and 5.

Such unevenness formation is caused by, for example, a decrease in the GaAs and Al ratio.
NH40H selectively etching GaAlAs:
A mixture of H202=20:1 is used at 40°C for several minutes. That is, in such an etching solution, the active layer 4 having a lower Al ratio than the second and third cladding layers 3 and 5, the substrate 1 made of GaAs, and the cap layer 6 are etched more than the first and second cladding layers 3 and 5. It is etched selectively due to its high speed. As a result, as shown in the figure, the side surfaces of the active layer 4 are connected to the first and second cladding layers 3 and 5 at the side surfaces 10a and 10b.
It will go inside from the side. Incidentally, during such etching, the end face of the resonator is covered with a non-etching mask against the etching solution.

According to the semiconductor laser of this embodiment, both sides 10
Even if a and 10b are clamped with tweezers, the impurities adhering to the tweezers are difficult to adhere to the etched active layer 4, so that no junction short circuit occurs due to natural diffusion of such impurities.

Further, even when the first electrode 8 side is bonded to a heat sink using solder, the creepage distance from the heat sink to the active layer is increased due to the taper of the cap layer 8, so short circuit accidents due to solder creeping up are reduced.

FIG. 2 shows another embodiment of the present invention, and the feature of this embodiment is that the two side faces 10a, 10 which are not the resonator end faces are
This is because the thickness of the active layer 4 near b is increased. Note that the same parts in FIG. 2 as in FIG. 1 are given the same numbers and their explanations will be omitted.

The reason for this configuration is that the layer thickness of the active layer 4 is normally very small at 0.1 μm, and therefore, in the configuration of the first embodiment, when the chip is crimped and fixed to a heat sink etc. with solder material, it bulges. This is because there is a problem that the liquid enters the recesses on the side surface of the active layer 4 due to capillary phenomenon, and the structure of this embodiment can prevent such intrusion due to capillary phenomenon.

In addition, as shown in FIG. 3, this embodiment device is an n-type
Grooves extending perpendicular to the plane of the paper are provided at regular intervals on one main surface of the GaAs substrate 1, and a first cladding layer 3, an active layer 4, a second cladding layer 5, and a cap layer 6 are formed on the one main surface. After successive lamination, an insulating layer 7 having striped openings between the grooves and first and second electrodes 8 and 9 are formed. Further, the surface shape of the first cladding layer 3 is made to substantially match the shape of one principal surface of the substrate, and the surface shapes of the other growth layers are flat.

After forming the electrodes, the chips are divided into chips along the grooves, and the two side surfaces 10a, 1
The chip shown in FIG. 2 is obtained by etching 0b with a mixture of NH40H:H202=20:1.

(f) Effects of the invention In the semiconductor laser of the invention, since the side surfaces of the active layer are deeper inside than the side surfaces of the first and second cladding layers on the side surfaces other than the resonator end faces, impurity diffusion and solder material creeping are prevented. Short circuits caused by uplinks can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the present invention;
3 and 3 are cross-sectional views showing other embodiments of the present invention. 3...first cladding layer (second semiconductor layer), 4
. . . active layer (first semiconductor layer), 5 . . . second cladding layer (third semiconductor layer).

Claims (1)

[Scope of utility model registration request] a first semiconductor layer sandwiching the semiconductor layer;
In a semiconductor laser including an oscillation layer having second and third semiconductor layers having a larger band gap and a smaller optical refractive index than the semiconductor layer, the semiconductor laser including the oscillation layer has resonance of the oscillation layer. A semiconductor laser characterized in that, on side surfaces other than the end surfaces, the side surface of the first semiconductor layer is deeper than the side surfaces of the second and third semiconductor layers.