JPS61185993A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a multi-wavelength semiconductor laser device by a method wherein said device is constituted by a method that at least the first clad layer and two or more sorts of compound semiconductor thin films of different compositions are stacked alternatively to form three or more layers. CONSTITUTION:Steps are made on a substrate made of compound semiconductor such as GaAs by etching, and a thin film multilayer region 9, in which two or more sorts of compound semiconductors such as a buffer layer GaAs 7 and AlXGa1-X As layer 8 of the first clad layer are stacked alternatively to form three or more layers, the second clad layer 10 and a cap layer 11 are formed in turns. A p-type metallic electrode Au/Zn layer 12 at a flat region and an n-type metallic electrode An/Su layer 13 at the substrate side are provided respectively and they are cleaved vertically in difference in level direction then become a reflecting face. Growth speed of an epitaxial growth layer is slow down in order of an upper flat region, difference in level region and a lower flat region. Since layer thickness of quantum well layer comes to be thin in the above-state order, oscillation wavelength have relationship as follows, lambda3>lambda5>lambda4 provided that, oscillation wavelength at the upper flat region is lambda3, said wavelength at difference in level flat region is lambda5 and said wavelength at the lower flat region is lambda4. A multi-wavelength semiconductor laser device, whose wavelength is different at each region, is obtained. Thereby, desiable multi-wavelength laser fitting to photosensitivity can be formed easily.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a semiconductor laser device used in the field of optical information processing.

2. Description of the Related Art In recent years in the field of optical information processing, semiconductor lasers have been used for reading and erasing data on optical disks and the like. Then, depending on the purpose, there are cases where it is desired to read immediately after writing, or cases where it is desired to write and read after erasing. In this case, the wavelength of the writing semiconductor laser light (λW
It is better that the reading wavelength (denoted as λR) is different from the reading wavelength (denoted as λW>λR). This is because these semiconductor lasers are placed close to each other, so to avoid mixing the writing signals during reading, and to make the reading signals accurate, the spot diameter of the reading laser beam must be adjusted. This is also to make it smaller (shorten the wavelength).

In addition, when recording high-definition television images, there is a desire to write luminance signals and color signals using separate laser wavelengths. Considering these considerations, there is an increasingly strong desire to integrate a plurality of semiconductor lasers with different wavelengths into a single chip.

Conventionally, in this type of semiconductor laser, normal double heterostructures as shown in Fig. 4 are stacked twice, and a part of the upper double heterostructure is removed to create a semiconductor laser for the lower double heterostructure. There are some that have electrodes formed for them (S
hiro 5akai; ElectranLcsL
eff, 1817 (19B2)).

Here, the electrode 5 for the active layer 1 and the electrode 4 for the active layer 3 serve as electrodes for laser driving. The electrode 3 is a common electrode, and is designed to emit a laser beam with an oscillation wavelength λ1 that drives the semiconductor laser in the current region, and to emit a laser beam with an oscillation wavelength λ2 when the semiconductor laser in the B region is driven. Ta.

Problems to be Solved by the Invention However, in such a structure, the material of the electrode 4 in the A region (for example, Au/Zn) and the material of the electrode 2 in the B region (Au/Zn) are different.
/Sn), it requires at least three electrode formation steps, and the process is complicated, such as the active region of each semiconductor laser being composed of a different epitaxial layer. Furthermore, a semiconductor laser whose active region is between electrodes 2 and 4 has inferior characteristics compared to a semiconductor laser whose active region is between electrodes 2 and 5 due to the influence of sheet resistance in P Fjl lnP. Therefore, the present invention provides an innovative multi-wavelength semiconductor laser device to solve these problems.

Means for Solving the Problems The technical means of the present invention for solving the above-mentioned problems is to provide at least a first cladding layer on a compound semiconductor substrate having a single or multiple step structure, and a binary or ternary cladding layer. A thin film multilayer region and a second cladding layer are formed by alternately stacking three or more layers of two or more types of compound semiconductor thin films having different compositions at least in terms of the elemental system, and a plurality of semiconductor laser devices with different oscillation wavelengths are integrated into a single layer. This allows it to be formed by multiple epitaxial growth steps.

For production The effect of this technical means is as follows.

As a result of research, the inventors found that when epitaxial growth is performed on a substrate having a step structure, the growth rate is different in the flat region and the step region, which results in a difference in the layer thickness of the layer. This phenomenon has almost no effect on the oscillation wavelength of conventional double heterostructure lasers, but it does
inyj! e-quantum well, 5QW
) type laser or multiple quantum well (mult L)
-quantum wel 1, MOW) type lasers, the thickness of the quantum well layer, which is an ultra-thin film, differs, and the oscillation wavelength of these quantum well type lasers depends on the thickness of this quantum well layer. The oscillation wavelength differs for each region. As a result, a multi-wavelength semiconductor laser device with different oscillation wavelengths can be realized in - times of growth steps.

Embodiments Hereinafter, embodiments of the present invention will be described based on FIGS. 1 to 3. In FIG. 1 showing a first embodiment of the present invention, a GaAg or other compound semiconductor substrate 6 is etched to provide a step, which is a buffer layer GaAs 7 and a first cladding layer. A ft EG a 1- rAs (!=0
．． 4) L2, thanks to the composition of layer 8 and film thickness of 10 to 200 people
A thin film multilayer region in which 3 layers of seed deposits are alternately stacked, for example, A2A Ga1-AAs (y = o
, 3) thin film multilayer region (SQ
W layer or MQW layer) 9, second cladding layer AX
The xGa 1xAg (x '' O-4) layer 10 and the cap layer GaAs 11 are sequentially formed by an epitaxial growth method.The forbidden band width of the semiconductor of the first and second cladding layers 8.1o is the widest forbidden band width of the thin film multilayer region. The stepped region is made into an electrically insulating isolation region 14 by removing the corresponding region by proton irradiation or etching, or by filling the etched region with silicon nitride, silicon oxide, or polyimide; The flat region is used as the active region of the semiconductor laser.The flat region has a P-type metal electrode such as A
The u/Z n layer 12 and the n-type metal electrodes, such as An/Snn/S gold layers, are provided on the substrate side by forming folds perpendicular to the step direction to form a reflective surface, as shown in Fig. 1. It becomes a semiconductor laser device.

As mentioned above, the growth rate of the epitaxial growth layer slows down in the order of the upper flat region 9 step region and the lower flat region, and as a result, the thickness of the quantum well layer becomes thinner in this order, as shown in Figure 3. The oscillation wavelengths have the following relationship: oscillation wavelength λ3 in the upper flat region> oscillation wavelength λ5 in the stepped region> oscillation wavelength λ4 in the lower flat region, and a multi-wavelength semiconductor laser device having different wavelengths in each region is obtained. 11th
The semiconductor laser device shown in the figure uses the step region as an electrically insulating isolation region, so the oscillation wavelength is λ3゜λ2.
Become a type.

A second embodiment of the invention will be described based on FIG. The structure of the epitaxial growth layer is the same as in the first embodiment, but both the flat region and the nine step regions are used as active regions of the semiconductor laser, and the vicinity of the boundaries of each region are electrically insulated and isolated using the same method as in the first embodiment. and form an electrode. In this example,
For a single step, three types of semiconductor lasers with different wavelengths can be produced by - times of epitaxial growth. Furthermore, it is clear that by applying the structure of the present invention to a substrate on which a plurality of steps are formed, semiconductor lasers with even more wavelengths can be formed at the same time.

1st. The semiconductor laser device shown in the second embodiment has An, G
a1-, As/GaAg system as well as In
It can also be applied to GaAsP/InP systems. Second
In this embodiment, since the angle of the step can be freely changed for the emission pattern in the step area, for example, in the case of a right-angled step, an emission pattern rotated by 90 degrees can be easily obtained in the step area compared to the emission pattern in the flat area. In addition, thin film multilayer regions, etc. are formed using metal organic chemical vapor deposition (MOCVD).
: metal organic chemical
It may be formed by a vopor deposition, or other forms are possible.

Effects of the Invention As described above, according to the present invention, a plurality of semiconductor lasers with different oscillation wavelengths can be easily formed on one chip, so it can be applied to laser arrays for optical disks, etc., and moreover, the laser array can be formed by one epitaxial growth. Since it can be formed in a process, the manufacturing process is simple and laser arrays with extremely excellent characteristics can be manufactured with good reproducibility. In addition, since the oscillation wavelength can be freely controlled by controlling the thickness of the thin film multilayer region that is the active region, it is easy to form a desired multi-wavelength semiconductor laser that matches the photosensitive characteristics of the photoreceptor material, and these multi-wavelength semiconductor lasers It can greatly contribute to optical information processing systems using

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a semiconductor laser device according to a first embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a semiconductor laser device according to a second embodiment of the present invention, and FIG. 3 is a diagram showing a flat area. FIG. 4 is a diagram showing the structure of a conventional multi-wavelength semiconductor laser device. FIG. 6...N-type GaAs substrate, 8...First
Ground layer, 9... SQW or MQW layer, 1
o...Second ground layer, 1ze electrode, 14...
...Electrical insulation isolation area. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 13t @ Figure 3

Claims (6)

[Claims] (1) Three layers of at least a first cladding layer and two or more types of compound semiconductor thin films with different compositions such as binary or ternary or more are alternately formed on a compound semiconductor substrate having a single or multiple step structure. A thin film multilayer region and a second cladding layer configured by stacking the above are formed, and the first and second
A semiconductor laser device characterized in that the forbidden band width of the semiconductor in the cladding layer is equal to or wider than the widest forbidden band width of the semiconductor in the thin film multilayer region. (2) The semiconductor laser device according to claim 1, wherein the stepped region is used as an electrically insulating isolation region, and the flat region other than the stepped region is used as an active region of the semiconductor laser. (3) The semiconductor laser according to claim 1, characterized in that both the stepped region and the flat region other than the stepped region are used as active regions of the semiconductor laser, and the vicinity of the boundary of each region is electrically insulated and isolated. Device. (4) A patent claim characterized in that the electrical insulation isolation is performed by proton irradiation or removal by etching of the semiconductor region corresponding to the electrical insulation isolation region, or by filling the etched removal region with silicon nitride, silicon oxide, or polyimide. The semiconductor laser device according to the range 2 or 3. (5) The compound semiconductor substrate having a step structure is made of GaAs.
The semiconductor laser device according to claim 1, wherein the semiconductor laser device is a substrate. (6) The semiconductor laser device according to claim 1, wherein the thin film multilayer region is formed by metal organic vapor phase epitaxy.