JPS5832481A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To manufacture easily a favorable semiconductor laser element having favorable reproducibility by a method wherein at the prescribed conductive type semiconductor multilayer structure containing the laser active region, at least the two mutually independent semiconductor diffusion regions are provided from the upper face. CONSTITUTION:An N type Ga0.5Al0.5As layer 2, an N type Ga0.9Al0.1As active layer 3, an N type Ga0.5Al0.5As layer 4 are made to grow in order on an N type GaAs substrate 1 according to the usual liquid phase growth method. Then an Si3N4 film 6 is formed on the surface of crystal, windows 9 of 3X3mum<2> size are opened at the 12mum pitch on a straight line, and Zn is made to be diffused in the front side of the active layer. The heat treatment is performed to make Zn to be diffused being extended up to make the diffusion front to reach in the layer 3 or the layer 2, and the P type semiconductor regions 5 are formed. After then a Cr-Au electrode 7 is formed on the surface 10, and an Au-Ge-Ni electrode 8 is formed on the back. A cleavage is performed to form a cleavage plane 20, and a chip is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser device, and more particularly, to a double heterostructure semiconductor laser device.

Semiconductor lasers are made of semiconductors, such as gallium arsenide (GaA
The substrate is a single crystal such as 1), has an active layer sandwiched between substances with different forbidden band widths in a double heterostructure, and is further formed so that the junction plane for current injection intersects with the heterojunction plane. The so-called transverse junction and strife (generally within Ty) lasers have the advantage that the threshold current for oscillation is low and single-longitudinal mode and fundamental transverse mode oscillations are easily obtained. TJS lasers are also characterized by a small oscillation spot size.If this spot size is small, the oscillation density at the cavity end face becomes high, and continuous operation will cause specular damage and deteriorate the laser operation. It has been known.

In particular, among the deterioration phenomena of a semiconductor laser that depend on the optical output, the most important one is the deterioration of the end facet.

Regarding the phenomenon in which the end face is instantaneously destroyed when the optical output increases, it has been reported that when the vicinity of the end face is made transparent, the critical optical output for destruction increases significantly. The method of making this end face transparent is to diffuse Zn into the active layer except for the vicinity of the end face, shift the oscillation wavelength to the long wavelength side by an amount corresponding to the impurity level, and make the vicinity of the end face (where Zrl is not diffused) Methods such as making the device transparent or embedding transparent crystal near the end face have been used, but these methods require precise control and the manufacturing method is complicated, making it difficult to create devices with good characteristics. It was extremely difficult to produce with good reproducibility.

An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a device structure that enables a high-output semiconductor laser device with a simple device fabrication process, good reproducibility, and good optical quality.

In order to achieve the above objects, the present invention has a structure in which, in a semiconductor multilayer structure of a predetermined conductivity type (for example, n conductivity type) including a laser active region, at least two semiconductor diffusion regions are formed independently from each other from the top surface. In the present invention, it is important to provide the above-mentioned diffusion region along the direction in which light travels. In particular, it is important that at least one side of the planar pattern of the diffusion region is parallel to the light traveling direction. It is sufficient that the diffusion regions are provided along the traveling direction, and the same effect can be obtained even if the diffusion regions are not arranged in a straight line. Further, the size of the diffusion region may be different.Furthermore, the plane pattern of the diffusion region may be triangular, rectangular, polygonal, etc., as long as at least one side is parallel to the light traveling direction, the other side is Even if it is curved, it can be applied without any difference and the same effect can be obtained. In either case, it is important that the plane pattern of the above-mentioned diffusion region is provided away from the laser output light end face (general Vc arm opening face).

Since the present invention has the above-described configuration, a PNN junction shape is formed around the diffusion region. As mentioned above, in a semiconductor multilayer structure including a laser active region, there are PNs in the laser active layer along the direction of light propagation, except for the vicinity of the end face of the laser.
A large number of joint surfaces are formed. Laser oscillation is obtained by the light generated at these many p-n junctions. In this structure, a pantotile is formed in the diffusion part where Z" is diffused with impurities, and the laser oscillation wavelength shifts to the long wavelength side, so the Z"
The vicinity of the end face where n is not diffused becomes transparent to the oscillation wavelength, and deterioration of the end face can be reduced. The same applies to other regions where zn is not diffused. In this way, this structure has the characteristic that electrons are injected into the laser active region from all the boundaries between the 7,n diffusion region and the non-diffusion region in the active layer internal pressure, so the %Zn diffusion front is activated. It does not need to stay precisely in the layer and can penetrate through the active layer. In other words, it is easy to control the diffusion, which greatly simplifies the device fabrication process. It can be made.

Further, in the present invention, since the semiconductor diffusion regions are arranged in parallel in the light traveling direction, laser oscillation is performed in a straight line at a place where the gain is greatest, that is, on an extension to an end face including a straight line part. It happens.

Here, since the wavelength of light generated at the p-n junction formed in the semiconductor layer is mainly emitted through the Zn level as described above, the energy gap of the non-diffusion part of the semiconductor layer is The wavelength corresponds to a small amount of energy. Therefore, the unexcited portion near the end face is substantially transparent to this wavelength, allowing light to propagate without loss of absorption.

As a result, since light absorption at the end face is small, deterioration due to damage to the end face, which is a common problem in conventional semiconductor lasers, is less likely to occur, and a large optical output can be achieved. In addition, according to this structure, the G town-A At A Al (0≦y≦1) layer is generally called the active region, but in reality, it is the first region of p0 conductivity type due to Zn diffusion and the above-mentioned Zn. It is divided into three parts: a second region of p-conductivity type formed by stretching diffusion and a third region of n-conductivity type up to the original t, and the boundary between the second and third regions, that is, the PN junction region. is sometimes called an active region in a narrow sense. 1) -Ga, -A which becomes the active region in the above narrow sense
/, In the As region, the n1 high concentration p region (p
Since the refractive index is slightly larger than that in 9), the transverse mode is also stabilized.

In this example, the X-wing: 0.6. Y! 0.2, we were able to obtain a laser with transverse fundamental mode oscillation with an oscillation wavelength of 7501 m and a threshold current value @ 150"A% optical output toomw or more.

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a schematic cross-sectional view of a semiconductor laser device according to an embodiment of the present invention in the direction in which laser light travels. 1 is n
With a type Ga substrate (Si doped, n~2X10"i),
By the usual liquid phase growth method, noa, , Am, ,
AI layer ('re doped, n ~ 5 x 10''13-''
, thickness 3 films m)2, "-G"o, @ At6. IA
I active layer (Tl doped, n-1X IO" an-
1 thickness ~ 0゜2/Jm) 3, "-G"o, sA4+, B
An Am layer (Te doped, n-5x10m?tM-', thickness ~2 μm) 4 was grown sequentially.

Next, six films of S-N were formed on the crystal surface, and windows 9 of three films and 3 μml were opened in a line at a pitch of 12 μm as shown in FIG. 2, and Zn was diffused in front of the active layer. In addition, the area near the end face of the laser element is approximately 107! A first heat treatment is performed to form a non-diffusion region, and then the zn diffusion (7 o 7) is stretched and diffused until it reaches the active layer 3 or the "-G" o-s AtO,s A" layer 2. (generally referred to as drive-in or simply diffusion) to form a p-type medium conductor region 5.

After that, a 10VcC1r-ALI electrode 7 is formed on the surface,
An Au-()e-N'i electrode 8 is formed on the back surface. Next, cleavage is performed to form a cleavage plane 20, and a resonator length 30 is formed.
A 0 μm chip was fabricated.

In addition, Fig. 1 shows the traveling direction of the light, that is, Fig. 2 x-x.
' is a sectional view at '.

In this structure, the refractive index of the part 5 where Zn is diffused in the active layer becomes a little larger, so a light waveguide effect also occurs in the horizontal plane with respect to the active layer 3, and the laser oscillation mode is also stabilized. . This laser has a threshold current value of about 150 mA, and a stable oscillation mode up to 100 mW or more was obtained. Reliability has also been significantly improved because the exposed end faces are transparent.

In addition, in this structure, the depth of the semiconductor diffusion region 5 is equal to the depth of the active layer 3.
It is only necessary to penetrate the ZN diffusion depth, and it is not necessary to precisely control the ZN diffusion depth.The device manufacturing yield has been significantly improved.

FIG. 3 is a schematic plan view of a semiconductor laser device as another embodiment of the present invention. The cross-sectional view in the direction of light propagation is the same as that of FIG. 1. In the present invention, the ZN diffusion windows 9 are alternately staggered.

Therefore, the gain is greatest in the portion where the diffusion windows overlap when viewed in the direction of light travel. However, in general,
Since the impurity diffusion region is formed larger than the diffusion window 9, the oscillation mode is stabilized in the overlapping area.
In the present invention, a stable oscillation mode can be similarly obtained even when the lateral diffusion of sZ'' is even larger.

FIG. 4 is a cross-sectional view along the direction of light propagation, similar to FIG. 1, showing still another embodiment of the present invention. 1 in the same figure
8 are similar to the embodiment shown in FIG. 11 is P-GJl
o, s A4, t A1 layer (Ge doped, 1)
~5X1G"m, thickness approximately 0.6m), 12 is n-Q
In the zero-strand structure, which is an IAI layer (Sfl doped n~5X10"cm-", thickness about 0.4μm), s, Z''
In the case of the first embodiment, the current is blocked in the part where the diffusion is not done by the effect of the p-n junction with a large barrier potential between layer 4 and layer 11 and the p-n reverse bias between layer 11 and layer 12. The dielectric band film 6 as shown in FIG. Therefore, according to the present structure, heat dissipation is further improved, and reliability is further improved. The rest is the same as in FIG. 1, so detailed explanation will be omitted.

In this example as well, the diffusion windows could be arranged in the same manner as in the previous example, and the same effect could be obtained without any difference. In addition, in the above embodiment, the planar pattern of the diffusion window was a square, but it can of course be rectangular if at least one side of the diffusion window is parallel to the light traveling direction.
Triangles or other polygons could also be used in the same manner with the same effect.

As explained above, according to the present invention, it is sufficient to provide a plurality of mutually independent Zn diffusion regions along the light traveling direction, and 7. A high output, highly reliable semiconductor laser can be obtained without the need to precisely control the diffusion depth of n, etc. Further, although the current inflow method of the present invention can be modified individually by combining it with other materials or semiconductor lasers with other structures, these do not depart from the scope of the present invention. The technical effects of this are significant. Furthermore, by controlling the diffusion width, it is possible to control the longitudinal mode.・

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a semiconductor laser device according to an embodiment of the present invention in the direction of propagation of light, FIG. 2 is a schematic plan view of FIG. 1, and FIG. FIG. 4 is a schematic plan view of a semiconductor laser device as yet another embodiment of the present invention.

Claims (1)

[Claims] 1. A semiconductor substrate, a first semiconductor layer of a first conductivity type formed on the substrate, and a semiconductor layer of a first conductivity type formed on the layer having a narrower forbidden band width than that of the layer. a second semiconductor layer, a third semiconductor layer of a first conductive layer having a wider forbidden band width than the second layer formed on the second semiconductor layer, and a third semiconductor layer formed on the second semiconductor layer; In the semiconductor laser device, the semiconductor region has a second conductivity type semiconductor region formed continuously so as to reach the second conductivity type, and an electrode formed in contact with the first and second conductivity type regions. What is claimed is: 1. A semiconductor laser device comprising two regions arranged in the direction of light propagation. 2. The semiconductor laser device according to claim 1, wherein the semiconductor region has a planar pattern in which at least one side is parallel to the light traveling direction.