JPH088218B2 - Method for forming compound semiconductor thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epitaxial growth method for laminating a compound semiconductor thin film having a quantum well structure on a compound semiconductor substrate having a step.

[0002]

2. Description of the Related Art Recently, in the field of optical information processing, optical
Optical recording and reproducing devices such as discs have come to be used
There is. Writing data to this optical recording / reproducing device
A semiconductor laser for reading, erasing and erasing is used. So
Depending on the application, if you want to read immediately after writing,
Write or read while erasing
There are times when you want to stay. In this case, the semiconductor laser for writing
The wavelength of light (λ_WAnd a semiconductor laser for reading
Wavelength of light (λ_RShould be different (λ_W>
λ _R). Because these laser diodes are placed close to each other.
Since it is placed, the signals at the time of writing are mixed at the time of reading.
This is to avoid the evil, and the signal when reading is accurate
Therefore, the spot diameter of the laser light for reading is reduced.
This is also to (to shorten the wavelength).

In addition, even when recording a high-definition television image, there is a desire to write a luminance signal and a color signal with two types of laser beams having different wavelengths. Under such circumstances, in recent years, there has been an increasing demand for integrating a plurality of semiconductor lasers having different wavelengths into one chip. Further, a semiconductor laser device that emits a plurality of laser beams is strongly desired as a light source for optical multiplex communication for performing large capacity communication.

Conventionally, as a one-chip semiconductor laser capable of emitting a plurality of laser beams, a normal double hetero structure as shown in FIG. 4 is laminated twice, a part of the upper double hetero structure is removed, and the lower double hetero structure is removed. There is one in which electrodes for a semiconductor laser for a double hetero structure are formed (Shiro Sakai; El
ectronics Lett. 18 17 (1982)).

In this semiconductor laser, the electrode 5 for the active layer 1 and the electrode 4 for the active layer 3 are electrodes for driving the laser, respectively. The electrode 3 is a common electrode, and when the semiconductor laser in the area A is driven, the laser light having the oscillation wavelength λ ₁ is emitted, and when the semiconductor laser in the area B is driven, the laser light having the oscillation wavelength λ ₂ is emitted. (Λ ₁ ≠
λ ₂ ).

[0006]

However, in such a structure, the material of the electrode 4 in the A region (for example, Au / S) is used.
n) and the material (Au / Zn) of the electrode 2 in the B region require at least three electrode formation steps, and the process such that the active region of each semiconductor laser is composed of different epitaxial layers is complicated. There was a difficulty that became.

Therefore, the present invention solves these difficulties.
A method for forming a compound semiconductor thin film is provided.

[0008]

The technical means of the present invention for solving the above-mentioned problems is to provide at least a first flat area,
A compound semiconductor substrate having a second flat region formed closer to the substrate than the first flat region via a step region.
On top of that, by performing one epitaxial growth,
In the tongue area and said second flat regions, two or more compound semiconductor thin film having different binary or ternary or more compositions are laminated by epitaxially grown so that the quantum well layer structure, the second The compound semiconductor thin film on the first flat region has a thickness different from that of the compound semiconductor thin film on the second flat region.
A method for forming a semiconductor thin film .

The film thickness of the compound semiconductor thin film on the step region is between the film thickness of the compound semiconductor thin film in the first flat region and the film thickness of the compound semiconductor thin film in the second flat region.

[0010]

The function of this technical means is as follows.
As a result of research, the inventors have found that when epitaxially grown on a substrate having a step structure, the growth rate is different between the flat region and the step region. That is, as a result, the layer thickness of each growth layer is different in each region.

A single-quantum well (SQW) or a multi-quantum well (MQW) in which ultrathin films are alternately stacked on a substrate has a quantum well layer which is an ultrathin film. It will be different. That is, a compound semiconductor layer having a quantum well structure having a different film thickness can be epitaxially grown in one growth step.

[0012]

EXAMPLE An example in which a semiconductor laser device is manufactured by using the epitaxial growth method of the present invention will be described below with reference to FIG.
~ It demonstrates based on FIG.

(Embodiment 1) In FIG. 1 showing a first embodiment of the present invention, a step is formed on a compound semiconductor substrate 6 such as GaAs by etching, and a buffer layer GaAs 7 and a first layer are formed on the stepped semiconductor substrate 6. Al that is the clad layer
_x Ga _1-x As (x to 0.4) layer 8 and film thickness 10 to 20
A thin-film multilayer region in which two or more kinds of compound semiconductors having different compositions of 0 Å are alternately stacked to form three or more layers, for example, Al _y Ga.
_1-y As (y to 0.3) layer and a GaAs layer, a thin film multilayer region (SQW layer or MQW layer) 9, and a second cladding layer of Al _x Ga _1-x As (x to 0. 4) Layer 10,
The cap layer GaAs11 is sequentially formed by the epitaxial growth method. The forbidden band width of the semiconductor of the first and second cladding layers 8 and 10 is the same as or wider than the widest forbidden band width of the thin film multilayer region.

The step region is used as an electrically insulating isolation region 14 by removing the corresponding region by Protonton irradiation or etching or by filling the etching removed region with silicon nitride, silicon oxide or polyimide, and using the flat region as the active region of the semiconductor laser. .
In the flat region, a P-type metal electrode such as Au / Zu layer 12,
An n-type metal electrode, for example, an An / Sn layer 13 is provided on the substrate side and is cleaved perpendicularly to the step direction to form a reflection surface, whereby a semiconductor laser device as shown in FIG. 1 is obtained.

As described above, the epitaxial growth layer is formed.
Long velocity is in the order of upper flat area, step area, and lower flat area.
As a result, the quantum wells are delayed in this order, as shown in Figure 3.
Since the thickness of the door layer is thin, the oscillation wavelength is in the upper flat region.
Oscillation wavelength λ₃> Oscillation wavelength λ in step region_Five＞ Below
Wavelength λ in flat area_FourBecome a relationship,
A multi-wavelength semiconductor laser device with different wavelengths in
It The semiconductor laser device shown in FIG.
Since it is used as an edge separation region, the oscillation wavelength is λ ₃, Λ_Four
There are two types.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. The structure of the epitaxial growth layer is the same as that of the first embodiment, but the flat region and the step region are both active regions of the semiconductor laser, and the vicinity of the boundary between the regions is electrically isolated by the same method as in the first embodiment. Then, the electrodes are formed. In this embodiment, three kinds of semiconductor lasers having different wavelengths can be formed by a single epitaxial growth for a single step. By applying the configuration of the present invention on a substrate having a plurality of steps formed thereon, it is apparent that semiconductor lasers having more wavelengths can be formed at one time.

The semiconductor laser devices shown in the first and second embodiments are, of course, Al _x Ga _{1 -x} As / GaAs type and I type.
It can also be applied to the nGaAsP / InP system. In the second embodiment, since the emitting pattern in the step region can freely change the angle of the step, for example, in the step region, the angle is 9 in the flat region as compared with the emitting pattern in the flat region.
An emission pattern rotated by 0 ° can be easily obtained. In addition, the thin-film multi-layer region and the like are formed by metal organic chemical vapor deposition (MOCVD:
Organic chemical vapor deposition) or other known growth methods such as MBE (Molecula).
It can also be formed by the r Beam Epitaxy method.

[0018]

As described above, according to the present invention, a compound semiconductor thin film having a quantum well structure having a different film thickness can be formed on a substrate by a single epitaxial growth step. A device with a simple manufacturing process and extremely excellent characteristics can be manufactured with good reproducibility.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a semiconductor laser device which is an embodiment using the present invention.

FIG. 2 is a diagram showing a configuration of a semiconductor laser device which is an embodiment using the present invention.

FIG. 3 is a diagram for explaining a relationship between a layer thickness of a thin film multilayer region and an oscillation wavelength in each of a flat region and a step region.

FIG. 4 is a diagram showing a configuration of a conventional multiwavelength semiconductor laser device.

[Explanation of symbols]

 6 n-type GaAs substrate 8 first cladding layer 9 SQW or MQW layer 10 second cladding layer 12 electrode 13 electrode 14 electrically insulating isolation region

Claims (2)

[Claims] 1. At least a first flat region and the first flat region.
Through the step region from a flat region on a compound semiconductor substrate and a second flat region formed on the substrate side of the, by a single epitaxial growth, the first flat region
And the said second flat regions, two or more compound semiconductor thin film having different binary or ternary or more compositions are laminated to epitaxially so that the quantum well layer structure
It is the first compound film thickness of the semiconductor thin film on the flat area, formed of the compound semiconductor thin film characterized by be epitaxially grown as different from the thickness of the compound semiconductor thin film on the second flat region Way . 2. A compound thickness of the semiconductor thin film on the stepped region is between a film thickness of the compound semiconductor thin film on the first flat region, with a second compound film thickness of the semiconductor thin film on the flat region The compound according to claim 1, characterized in that
Method for forming semiconductor thin film .