JPH0638535B2 - Integrated semiconductor laser device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an integrated semiconductor laser device, and more particularly to an integrated semiconductor photodetector for monitoring each laser beam from the integrated semiconductor laser device. The present invention relates to an integrated semiconductor laser device.

[Technical background of the invention and its problems]

An integrated semiconductor laser device in which semiconductor laser devices having various oscillation wavelengths or essentially the same wavelength are formed on the same substrate is very useful for multiplexing communication in optical fiber communication or bit parallel transmission. Device. Further, if an integrated semiconductor laser device is used in a laser beam printer using a semiconductor laser, it is possible to simultaneously sweep several lines and achieve high speed. Furthermore, if the integrated semiconductor laser device is used as a light source for an optical disk pickup, Also, it is possible to write and read several lines almost at the same time. In this respect, the integrated semiconductor laser device is considered to be very useful in the fields of optical information processing and optical information transmission.

By the way, in this kind of integrated semiconductor laser device, how to monitor the optical output of each semiconductor laser element becomes a very important issue. In general, the current-light output characteristics of a semiconductor laser device are sensitive to temperature. Therefore, in order to keep the light output of each device constant, the light output of each device is monitored and each device is controlled to have a constant light output. It is necessary to adjust the current to flow. In addition, the current of each element-
Since the optical output characteristics change, it is absolutely necessary to monitor the optical output to compensate for this. However, in many cases, each element in the integrated semiconductor laser device is 50 [μ
m] to about 500 [μm] and the beam divergence angle of the laser light emitted from the semiconductor laser element is as wide as several tens of degrees, so that it is a little away from the integrated semiconductor laser device. When trying to detect the optical output with, the adjacent laser lights are mixed with each other, and as a result, the respective optical outputs of the semiconductor laser device cannot be properly monitored.

For monitoring the optical output of the semiconductor laser device, for example, GaA
In the case of As laser, a silicon photodiode is used. When the optical output of the integrated GaAAs laser is to be monitored by using this, silicon photodiodes are integrated in an array form, and they are mounted sufficiently close to the integrated GaAAs laser. In order to monitor the optical output of each of them independently of each other without interference, it is necessary to mount the silicon photodiode array within the distance between each laser element or less, but in many cases the mounting restrictions of the semiconductor laser element are restricted. Due to the conditions, they cannot be mounted close together.

As a means for solving such a problem, the inventors of the present invention have mounted a semiconductor laser element and a semiconductor photodetection element in a layered manner and mounted the light emitted from a rail element on a light-receiving surface parallel to the crystal plane of the laser element. I considered a method of receiving light with
51-83872). However, this method is effective for monitoring laser light from a single laser element, but has the following problems when applied to an integrated semiconductor laser device. That is, as described above, since the distance between the respective elements in the integrated semiconductor laser device is around 50 to 500 [μm], the structure is naturally monolithic. in this case,
Since the laser elements are very close to each other, the heat generated in one element raises the temperature of the adjacent element, and the current-light output characteristics of the lathe element have temperature dependence. Mutual interference of heat occurs between the laser elements, that is, the optical output of the laser elements varies. Then, it has been found that the mutual interference effect of heat is an unavoidable problem in the monolithic laser array.

Further, there is the following problem as another problem.

The individual laser elements of the laser array as described above are the third
As shown in the figure, a groove 39 reaching a position deeper than the pn junction is formed for electrical isolation between elements. When mounting on a silicon photodiode, the surface on which the groove is formed is mounted downward. To do. Also, as shown in FIG. 4, since the silicon photodiode array also performs electrical isolation,
After all, a deep groove 29 is formed. When the laser array and the photodiode array are integrated, the light emitting portion is mounted downward, that is, the electrical isolation grooves 39 and 29 are aligned so as to improve the heat dissipation characteristics. At this time, In, AaSn, or the like is used as the fusion metal, but the fusion metal may fill the V groove and impair the electrical separation. Further, the work is extremely difficult when the fusion metal is selectively adhered between the elements.

[Object of the Invention]

In view of the above-mentioned drawbacks, the present invention provides an integrated semiconductor laser device having good heat dissipation characteristics and including simple steps that do not require a step of depositing a fusion metal at the same intervals as each element. is there.

[Outline of Invention]

In order to suppress the mutual heat interference effect between the laser elements described above, the present invention does not use a fusion metal as a structure that allows heat to escape faster, and also includes electrode metals 28 and 38 that react with the fusion metal to increase the heat resistance. It has a structure in which the polished surface is directly bonded without using it, and the thermal resistance is reduced, and the structure is simplified by omitting the conventional step of selectively adhering the fusion metal.

〔The invention's effect〕

The heat dissipation characteristics of the integrated semiconductor laser device according to the present invention can greatly improve the heat dissipation characteristics obtained by the conventional mounting method, and the heat resistance thereof is reduced to a fraction. Further, it is possible to prevent a short circuit between the elements due to the fusion metal without requiring selective adhesion of the fusion metal, and the yield is improved.

Example of Invention

FIG. 1 is a perspective view showing a schematic structure of an integrated semiconductor laser according to an embodiment of the present invention. The device of this embodiment is an example in which a GaAAs laser array is used as an integrated semiconductor laser device and a silicon PN photodiode array is used as an integrated semiconductor device. In the figure, 10 is a copper stem,
An integrated semiconductor photodetection element 20 is mounted on the stem 10, and an integrated semiconductor laser element 30 is mounted on the photodetection element 20 .

Here, the semiconductor photodetector element 20 is, as shown in FIG.
A pn photodiode including an i substrate 21, an n layer 22, and a p layer 23 formed by diffusion. Each photodiode element is 30
The area of each light receiving portion 24 is 150 μm × 150 μm because they are electrically separated by deep grooves reaching the i layer provided at intervals of 0 μm.
It has become m. N-electrode 60 and p of each photodiode
The electrodes 26 are independent of each other, and as will be described later, the n electrode 60 of the photodiode is the p electrode of each element of the laser array.
It becomes common with the electrode.

On the other hand, the semiconductor laser device 30 includes an N-type GaAs substrate 3
1, N-GaAAs cladding layer 32, GaAs active layer 33, P-GaAAs cladding layer 34 and P-GaA
A laser having a heterojunction structure composed of the s contact layer 35 and the like is integrated.
[Μm]. The N-side electrode 36 of this laser serves as a common electrode, and the P-side serves as a common electrode with the n-side electrode 60 of the photodiode by mounting as described below. That is, the P-side-GaA of the semiconductor laser array shown in FIG.
The metal surface is not attached to the surface 37 of the s contact layer and is kept clean after mirror-polishing. The mirror-polished clean surface 2 shown in FIG. 6 is provided with no photodiode electrode.
7 is bonded together with the groove provided for electrical isolation described above.

The process of forming the element wafer by the direct bonding method is as follows. First, the adhered surfaces of the two semiconductor substrates are mirror-polished to form a surface roughness of 500 Å or less. Then, depending on the surface condition of the semiconductor substrate, pretreatment for degreasing and stain film removal is performed. In the case of a Si substrate, this pretreatment is, for example,
A process such as H ₂ O ₂ + H ₂ SO ₄ → royal water boil → HF is performed. After that, the substrate is washed with clean water for several minutes, and dehydrated by spinner drying at room temperature. This dehydration treatment is for removing the water that is excessively adsorbed on the mirror-polished surface, and it is important to avoid heating and drying at 100 ° C. or higher where most of the adsorbed water vaporizes. After that, the two substrates are bonded to each other in a clean atmosphere of class 1 or less in a state where substantially no foreign matter is present, and heat-treated at 200 ° C. or more. Si
In the case of a substrate, the preferable heat treatment temperature is 1000 ° C to 1200 ° C.

By this operation, good adhesion can be achieved both in terms of electrical characteristics and heat dissipation characteristics, good workability without the need for a fusion metal, and good heat dissipation characteristics not including the high thermal resistance layer due to the reaction between the electrode metal and the fusion metal. An integrated laser structure is obtained.

[Brief description of drawings]

1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. 6 are views for explaining the present invention. In the figure, 10 ... Stem, 20 ... PN photodiode array (integrated semiconductor photodetector), 22 ... N-type layer, 21 ...
... I layer, 23 ... P layer, 24 ... light receiving surface, 28, 36 ...
... N-type electrode, 26, 38 ... P-side electrode, 30 ... GaA
As laser array (integrated semiconductor laser device), 31
... N-type GaAs substrate, 32,34 ... cladding layer, 3
3 ... Active layer, 35 ... Contact layer, 27, 37 ...
Mirror-polished surface, 29, 39 ... Element separation groove, 40 ... Gold-tin alloy (fusion metal), 60 ... Common electrode.

Claims (1)

[Claims] 1. An integrated semiconductor laser device formed by integrating a plurality of laser devices on the same chip, and a plurality of photodetection devices integrated on the same chip, which are parallel to a crystal plane of the semiconductor laser device. The light receiving surface side is fixed to the one main surface so that the light receiving surface is in contact with the main surface, and the light receiving surface projects outward from the emission end surface of the laser light emitted substantially parallel to the crystal plane of the semiconductor laser device. In this integrated semiconductor laser device, the integrated semiconductor laser is characterized in that the main surface and the light-receiving surface of the integrated semiconductor laser are dehydrated, bonded in a clean atmosphere, and then directly bonded by heat treatment. apparatus.