JPS61290788A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To realize a surface light-emitting laser enabling continuous oscil lations at room temperature by reflecting laser beams, which are emitted from a semiconductor laser element and projected to a photodetector, by an inclined end surface in the photodetector and changing the direction of laser beams. CONSTITUTION:A semiconductor laser takes an internal striped type in which an N-type GaAs current block layer 9 is formed onto a P-type GaAs substrate 2, currents are concentrated to a V groove section from which the block layer 9 is removed, and laser oscillations at a low threshold are conducted by an active layer 4 just above the V groove. Since the semiconductor laser has a P-N junction consisting of a P-type clad layer 3 and an N-type clad layer 5, the same structure is also used as a photodetector. Laser beams emitted from an end surface oppositely faced to the photodetector of the semiconductor laser are reflected by an inclined end surface in the photodetector, and projected in the direction vertical to a substrate surface. Photocurrents are generated by partial beams simultaneously projected to the photodetector, and monitor signals are acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser device used as a light source for optical communications and optical information processing equipment, and a method for manufacturing the same.

2. Description of the Related Art Semiconductor laser devices occupy an important position as light sources for optical communication systems and optical disks that enable high-density recording, and demand is expected to continue to increase in the future.

However, in most of the current semiconductor laser devices, the resonator is formed between the bones. Therefore, they inevitably become individual elements, which is not compatible with the integration of electronic devices, and is a major problem with semiconductor lasers.

Two methods of forming a resonator outside of the bone are shown in Figures 6A and B. One is a method using a distributed feedback reflector shown in FIG. 6A, which is called a DBR laser.
etat:AppliedphysicsLett
ers,vota29. p684 (1976)).

DBR lasers have a drawback in that they are extremely difficult to manufacture because a diffraction grating is built inside the semiconductor laser crystal. The other technique is to form the resonator end face by etching as shown in Figure 6B, which is relatively easy to manufacture and has a low threshold (
~30 mA) room temperature communication oscillation is possible. Various etching methods such as chemical etching and reactive ion etching have been tried. Recently, semiconductor lasers with end surfaces that are almost the same as the interosseous surfaces have been fabricated by chemical etching. (Wada et al.; Institute of Electronics and Communication Engineers Technical Research Report ED84-95.1984) By using end face formation technology by etching, an optoelectronic integrated circuit that integrates a semiconductor laser and an electronic element can be easily realized.

Incidentally, recently, with the aim of creating a two-dimensional array of semiconductor lasers, research has been carried out on surface-emitting lasers that emit laser light in a direction perpendicular to the Queue surface. (For example, Institute of Electronics and Communication Engineers Technical Research Report 0QE84-9.1984) Figure 6 shows G a
The structure of an As-line surface emitting laser is shown. The resonator is formed perpendicular to the epitaxial growth surface, and has advantages such as a short resonator structure with good longitudinal mode unity, and a large light emission spot, so the beam exit angle is narrow.

Problems to be Solved by the Invention However, for reasons such as the fact that the electrodes also serve as reflectors, the reflectance decreases due to the electrode alloy, and the difficulty of increasing the current density in the active layer, continuous oscillation at room temperature is not possible. Not yet reached.

The present invention aims to realize a surface emitting laser in which the resonator end face is formed by etching and is capable of continuous oscillation at room temperature.

Means for Solving the Problems The semiconductor laser device of the present invention includes a semiconductor laser element having a cavity end face formed by etching, and a photodetector in which the end face on the side facing the semiconductor laser element is inclined with respect to the cavity end face. If the device is not monolithically integrated, the laser beam emitted from the semiconductor laser element and incident on the photodetector is reflected by an inclined end face of the photodetector to change the beam direction. It consists of The cavity end face of the semiconductor laser device and the inclined end face of the photodetector are etched using a H2SO4-H2O based etching solution.

Operation With the above configuration, the semiconductor laser device of the present invention monitors the light emitted from the semiconductor laser element with a photodetector, reflects it at the inclination angle of the photodetector, and causes the light to travel in a direction at a certain angle from the substrate. It can be made into a surface emitting type semiconductor laser device. Further, the cavity end face of the semiconductor laser element and the inclined face of the photodetector are H2S04-H2O
At this time, the angle of inclination of the end face due to etching depends on the At mixed crystal ratio, so that the end face of the photodetector is inclined.

Embodiment FIG. 1 shows the structure of a surface emitting type etching cavity laser according to an embodiment of the present invention. Semiconductor laser is p-type G
It is an internal stripe type with an n-type GaAs current blocking layer 9 on the a A Ti substrate 2, and the current is concentrated in the V-groove portion where the blocking layer 9 has been removed, and low threshold laser oscillation is performed directly above the V-groove. This can be done with the active layer 4 of Further, since the semiconductor laser has a p-n junction consisting of a p-type cladding layer 3 and an n-type cladding layer 6, the same structure can also be used as a photodetector.

An end face 9 perpendicular to the active layer 4 is formed by etching as a resonator of the semiconductor laser. Laser light is emitted from both sides of the resonator, and in order to extract the laser light in a direction perpendicular to the substrate surface, the end face of the photodetector is etched at an angle of 46° to the heterojunction surface.

In this way, the laser light emitted from the end face of the semiconductor laser facing the photodetector is reflected by the inclined end face of the photodetector.

Emit light in a direction perpendicular to the substrate surface. At the same time, a portion of the light incident on the photodetector generates a photocurrent to obtain a monitor signal.

Laser light is also emitted from the other end facet of the semiconductor laser, but it may be used for other purposes, or if it is not needed, a high reflectance film may be attached to the end facet to prevent the laser light from being emitted.

FIG. 2 shows a simplified process for manufacturing the surface emitting laser of the present invention. The laser structure is an internal stripe type using a p-type GaAs substrate 2. As shown in FIG. 2A, a multilayer heterojunction is grown by liquid phase epitaxial growth. Next, a semiconductor laser and a photodetector are formed by etching.Using the fact that the inclination angle of the etched end face depends on the At mixed crystal ratio of each layer of the multilayer structure, the end face of the semiconductor laser is vertical and the photodetector is vertical. The end face of the vessel is 46
to °. That is, in the part where the semiconductor laser is manufactured, non-doped Ga0.5 is deposited on the n-type GaAs core tact layer 6.
Only the Ato, , As layer 11 is used, and the photodetector further includes a non-doped GaAs layer 12 and a non-doped Gao,
Etching is performed using a photomask 14 so that the As layer 13 becomes 5A (FIG. 2B). The etching solution is H.
2SO4-H2O2 system. Next, in order to form the end faces of the semiconductor laser and the photodetector, a photomask is attached again and etching is performed using the same etching solution. (FIG. 2C) At this time, it is utilized that due to the anisotropy of etching, the inclination angle of the interface changes depending on the At mixed crystal ratio at the interface of layers having different M mixed crystal ratios. In the part forming the end facet of the semiconductor laser, a GaAs layer 6 and a GaO, 5Ato, sAs layer are formed on the GaO, tsAto, 8As layer S.
Since there is layer 11, “o, J” and “o, s” including the active layer
Layers 5 and 3 can be perpendicular to the substrate plane.

However, in the part where the photodetector is manufactured, Gao, ts
l'hto, sAl! Since the layer 11 has a GaAs layer 12 and a Gao,5Ato,s'' layer 13, Gao,sA/!o,s in the portion where the semiconductor laser light is reflected
``Layers 3 and 54 can be formed at an angle of 45°. Because the end faces of the semiconductor laser and photodetector utilize the dependence of the crystal plane orientation of etching, it is possible to obtain flat end faces with very good properties. can.

Next, the photomask was removed, a Si3N4 film was applied to the entire surface by CVD, and the top layer 11 of the semiconductor laser and the third to third layers of the photodetector were removed by selective etching, and as shown in FIG. Complete with a 7. The end face of the semiconductor laser that does not face the photodetector may be coated with gold or the like to prevent laser light from being emitted.

FIG. 3 shows the current-light output characteristics of the semiconductor laser device in this example, and FIG. 4 shows the intensity distribution of the far-field image.

Effects of the Invention By using the semiconductor laser device and its manufacturing method of the present invention, a surface-emitting laser with good characteristics can be realized, and the development into optical ICs such as two-dimensional laser arrays is facilitated, and the effects are great. be.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a surface-emitting etching cavity laser which is an embodiment of the present invention, FIG. 2 is a sectional view showing the manufacturing process of an embodiment of the method of manufacturing a semiconductor laser of the present invention, and FIG. 4 is a current-light output characteristic diagram of a semiconductor laser device according to an embodiment of the present invention, FIG. 4 is an intensity distribution diagram of the far-field image, and FIG.
The figure is a structural diagram of a conventional DBR laser and an etching cavity laser, and FIG. 6 is a structural diagram of a conventional surface emitting laser. 1.7... Electrode, 3,5... Clad layer, 2... GaAs substrate, 4... Active layer.

Claims (4)

[Claims] (1) The semiconductor laser is formed by monolithically integrating a semiconductor laser element having a cavity end face formed by etching, and a photodetector whose end face on the side facing the semiconductor laser element is inclined with respect to the cavity end face. A semiconductor laser device characterized in that a laser beam emitted from a device and incident on the photodetector is reflected by an inclined end face of the photodetector to change the beam direction. (2) The semiconductor laser device according to claim 1, wherein the inclined end face of the photodetector is inclined at 45 degrees with respect to the heterojunction surface. (3) The cladding layer written on the semiconductor substrate is Ga_
A first GaAs layer and a first Ga_1_-_yAl_ are formed on the double heterostructure consisting of a 1_-_xAl_xAs layer.
Steps of sequentially forming yAs layers and the first Ga_1_
- selectively forming a laminated film of a second GaAs layer and a second Ga_1__yAl_yAs layer on the _yAl_yAs layer;
The surface of the s layer and the first Ga_1_-_yAlAs
A step of selectively applying a photomask to the surface of each layer, and a step of etching to a depth reaching the semiconductor substrate with an H_2SO_4-H_2O-based etchant to form a photodetector and a semiconductor laser on the semiconductor substrate. A method for manufacturing a semiconductor laser device, characterized by comprising: (4) The method for manufacturing a semiconductor laser device according to claim 3, wherein the photodetector has an end surface inclined at 45 degrees with respect to the semiconductor substrate.