JPH0252483A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To achieve a uniform carrier distribution on an activation layer and an efficient current injection by forming each conductive-type impurities area penetrating the activation layer selectively from both the left and right sides and forming a p-n junction in reference to an activation area making higher a conductivity of one clad layer. CONSTITUTION:After a semiconductor laser device forms a high-resistance AlGaAs layer 4 on a semi-insulating(SI) GaAs substrate 10, it forms a P-AlGaAs clad layer 3, a multiple-quantum well, namely a MQW activation layer 2, and an n-Al GaAs clad layer 1 in sequence. Then, a p-type impurities ion impregnation area 20 and an n-type impurities ion implantation area 21 are formed on these by the ion implantation method, respectively. The edge of an n-type impurities implantation area 21 and that of a p-type impurities implantation area 20 within an n-AlGaAs layer 3 are in AlGaAs junction with a high potential barrier, nearly no current flows, current flows through a p-n junction around the activation layer 2 with lower potential barrier than it, and carriers (in this case, electron) are injected into this activation layer 2. Thus, distribution of the carriers injected into this activation layer 2 becomes nearly uniform, thus achieving an efficient injection.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a semiconductor laser device and a method for manufacturing the same, and more particularly, to a high-performance semiconductor laser device and a method for manufacturing the same, which can be integrated as an optoelectronic integrated circuit (OEIG). This relates to its manufacturing method.

[Conventional technology]

The schematic configuration of each conventional semiconductor laser device suitable for integration with this type of electronic device is shown in the second section.
As shown in FIG.

That is, first, in the conventional configuration shown in FIG.
A semiconductor laser device uses a semi-insulating (Sl) GaAs substrate.
3. On top of the p-j2GaAs cladding layer. Multi-quantum well (Multi Quantum W) which becomes the active region
ell, MQW) layer 2. An n-811 GaAs cladding layer 1 and an n-GaAs contact layer 50 are sequentially formed, and then zinc (Zn) is selectively diffused to leave an n-type region in a stripe shape, and then a p-type region is formed. - A part of the n-GaAs contact layer 50 where the n-junction appears on the surface is selectively etched away, and electrodes 101 and 100 are formed on the remaining mouth-type and p-type surface areas, respectively. It is.

In the semiconductor laser device configured in this way,
The Zn spreading part in the MQW layer 2 as an active layer is disordered, and in this S, Al1Ga with an average composition is formed.
It is known that it becomes an As layer, and with this configuration,
A so-called buried laser structure is obtained.

Therefore, in the conventional configuration shown in FIG.
The p-n junction formed at the periphery of the non-disordered portion of the MQW layer 2, and the n-Al1G above it.
Two p- formed between aAs and the diffusion parts on both sides
Each of them will have an n junction, in this case,
The former p-n junction has a lower diffusion potential than the latter, so when a voltage is applied between the p and n electrodes, the current flows through the p-n junction around the active region where the potential is low. carriers are injected into the active region. As mentioned above, the peripheral part of this active region has a structure similar to that of a buried laser device, forming a so-called refractive index waveguide structure, so that its width allows only a single mode. If the width is narrow enough for propagation, a stable oscillation mode and a low threshold value can be obtained, and the surface level difference is relatively small, and both the p and n electrodes are formed on the same plane. This makes it suitable for integration with electronic devices.

In addition, in the semiconductor laser device having the conventional structure shown in FIG. 3, mouth-type and p-type impurity regions 21 and 20 are formed that reach up to the MQW layer 2, which is the active region sandwiched between the high-resistance AffiGaAs layers 1 and 3. , this is disordered as in the above, and in this case, the current flows through the p-type diffusion region 21
It flows from the side through the MQW active layer 2 to the n-type diffusion region 20 side. That is, in this case.

Although the current injection mechanism is slightly different, as in the case of the previous example, a semiconductor laser device with good characteristics and suitable for integration with electronic devices can be obtained with this method.

[Department notification that the invention attempts to solve]

However, in the structure of the conventional semiconductor laser device shown in FIG. 2, although current can be effectively injected into the active region, the difference in refractive index between the active region and the 11GaAs layer in the surrounding area is large. Because of its relatively large size, its width must be extremely narrowed to about 2 μm or less to obtain a single transverse mode, and a mouth-shaped electrode with low contact resistance is placed on top of this narrowed portion. It is extremely difficult to form a

On the other hand, in the conventional structure of the semiconductor laser device shown in FIG. 3, current is injected from the side to the active region, which causes carrier distribution and does not result in efficient injection. Moreover, the resistance value becomes high, and its continuous oscillation characteristics are limited.

Furthermore, in both of these conventional semiconductor laser devices, in order to effectively confine light in the active region, it is necessary to make the cladding layer relatively thick to about 2 μm or more, and it is necessary to make the cladding layer relatively thick by approximately 2 μm or more, which requires ion implantation of impurities. With this method, the implantation depth can only reach approximately 2 μm, so the disadvantage is that the impurity diffusion method, which has relatively poor workability and controllability, must be used to introduce this impurity. was there.

Accordingly, an object of the present invention is to improve these conventional problems. An object of the present invention is to provide a semiconductor laser device of this type and a method for manufacturing the same.

[Means for resolving burdens]

In order to achieve the above object, the semiconductor laser device according to the present invention has an active layer formed from both sides of the first . In a laser device having a three-layer structure sandwiched between second cladding layers, a semi-insulating region that is sufficiently thick compared to the spread of the electromagnetic field distribution in the waveguide mode is formed, and on this semi-insulating region, In this three-layer structure, impurity regions of different conductivity types penetrating the active layer are selectively formed from the left and right sides, and the conductivity of at least one cladding layer is increased to increase the conductivity between the active region and the active layer. In addition, the method for manufacturing a semiconductor laser device according to the present invention reduces the thickness up to the active layer in a three-layer structure, and also provides a substrate side for laser oscillation light. A transparent region is formed on the other hand, and impurity regions of different conductivity types can be introduced by ion implantation.

That is, the present invention provides an active layer having a thickness of 1000 Å or less, a single layer, or multiple quantum wells as the first layer.
a conductive type cladding layer; and a first cladding layer. A three-layer structure sandwiched from both sides by second conductivity type or high-resistance cladding layers is provided, and impurity regions of first and second conductivity types penetrating at least the active layer are provided in this three-layer structure. This is a semiconductor laser device characterized in that the active layer is selectively formed from the left and right sides to disorder the corresponding regions of the active layer, and the method of the present invention is characterized in that the electromagnetic field distribution of the waveguide mode is spread out. forming a sufficiently thick semi-insulating region, and forming an active layer of the first conductivity type on the semi-insulating region with a thickness of 1000 Å or less, or consisting of four layers or multiple quantum wells. a cladding layer, and a first cladding layer; a step of providing a three-layer structure with a thickness of 2 μm or less sandwiched from both sides by second conductivity type or high-resistance cladding layers; and selectively forming impurity regions of the second conductivity type from the left and right sides to disorder the corresponding regions of the active layer.

[For production]

Therefore, in the present invention, the active layer is first .
Then, impurity regions of different conductivity types penetrating the active layer are selectively formed from the left and right sides of the three-layer structure sandwiched between the second cladding layers, and the conductivity of at least one of the cladding layers is increased. Since a p-n junction is formed between the active region and the active region, a uniform carrier distribution can be brought about in the active layer, and efficient current injection can be performed.
In addition, by reducing the thickness up to the active layer in the three-layer structure,
Furthermore, since a region transparent to laser oscillation light is formed on the substrate side, an impurity region can be easily formed by ion implantation.

〔Example〕

Hereinafter, an embodiment of a semiconductor laser device and a method for manufacturing the same according to the present invention will be described in detail with reference to FIG.

FIG. 1 is a sectional view schematically showing the general structure of a semiconductor laser device to which this embodiment is applied. In the structure of the embodiment shown in FIG. Indicates the same or equivalent part.

That is, in the embodiment configuration shown in FIG. 1, the semiconductor laser device forms a high-resistance JI GaAs layer 4 on a semi-insulating (SI) GaAs substrate lO, and then forms a high-resistance JI GaAs layer 4 on the semi-insulating (SI) GaAs substrate lO. On the GaAs layer 4, p-Al1. Ga
As crat layer 3. MQW active layer 2 which becomes multiple quantum well
By sequentially forming row 11 GaAs cladding layers l and then using an ion implantation method from above, p-type impurity ion implantation regions 20. and an n-type impurity ion implantation region 21).In the ion implantation operation, heat treatment is often performed after the implantation in order to reduce crystal defects, etc., but in the case of this embodiment. Each impurity ion implantation region 20.2 in
1 also includes the region after the heat treatment to which impurities have migrated. When forming each of these impurity ion implantation regions 20.21, typical p-type impurity ions include Be, Mg, etc., and typical n-type impurity ions include Si, etc. , in particular but not limited to these. Furthermore, the MQW active layer 2 may be p-type, n-type, or undoped (light n-type or p-type).
In this case, it is assumed to be p-type.

In this embodiment, the MQW active layer 2 is disordered by ion implantation and has an average composition of 11GaAs, forming a refractive index waveguide structure similar to that of a so-called buried laser. In this state, when the width of the active layer 2 becomes approximately 2 μm or less, the waveguide propagates only the fundamental transverse mode, resulting in a stable oscillation mode. Although not shown in this case, since each electrode is selectively formed on the surface of each of these p-type and n-type impurity ion implantation regions 20 and 21, even if the width of the active layer 2 No matter how narrow the electrode is, it is possible to form an electrode of sufficient size, and there is no risk of causing the problem described in the conventional configuration shown in FIG. 2. In this case, even if a GaAs contact layer is provided under each electrode in order to obtain low contact resistance, as in the case of the conventional configuration shown in FIG. 2, other characteristics may be affected. There is no.

Therefore, in the case of this embodiment configured in this manner, the pn junction is formed by the following four consecutive parts.

That is, (1) the n-type impurity implanted region 21 in the p-Al1GaAs layer 1; (2) the active layer 2 and the n-type impurity implanted region 2;
(1) between the active layer 2 and the n-Affi GaAs layer 3; and (2) the p-type impurity implanted region @20 end in the n-^42 GaAs layer 3. Of these parts, the junction parts ■ and ■ become GaAs junctions with high potential barriers, so
Almost no current flows, but current flows through the p-n junction around the active layer 2, which has a lower potential barrier than this, and carriers (electrons in this case) are injected into the active layer 2. On the other hand, the width of this active layer 2 is about 2 μm at the navel, and the thickness is about 01 μm, so most of the current flows along this width.
The distribution of carriers flowing through the -n junction and injected into the active layer 2 becomes G-like, allowing efficient injection. And also in this case.

As long as a p-n junction is formed between the active layer and one cladding layer, the other cladding layer may be a high-resistance layer, and the conductivity types of the opposing cladding layers are also the same. Well, in the latter case.

Carriers are injected into the active layer mainly from two directions, upper and lower.

Therefore, as a means for obtaining the active layer structure,
There is an impurity ion implantation method, but as mentioned earlier, the implantation depth in this impurity ion implantation method depends on the type of ion and its acceleration voltage, but in normal cases, it is generally 2.
It is within the range of about .mu.m, up to 3 .mu.m at most. In addition,
Of course, there is an impurity diffusion method other than this impurity ion implantation method, but since this impurity diffusion method has poor workability and controllability, the impurity ion implantation method is used in this S.

In order to form the active layer structure by using the impurity ion implantation method in this way, at least MQW
Penetrating through the active layer 2, each impurity region 20.
It is necessary to form 21.

In other words, if the impurity ion implantation does not go beyond the underlying cladding layer l, a wide p-n junction will occur at the front, increasing parasitic capacitance and deteriorating the frequency characteristics. To form the active layer structure using the ion implantation method, these three layers 3.2. Each impurity region 20, 21 must be formed by penetrating through one structure.

Therefore, in order to satisfy the above requirements, in this embodiment, these three layers 3, 2 . The total thickness of the 3-layer structure and 3-layer structure is set within a range corresponding to the depth that can be implanted. The thickness of is Igm
Since the refractive index of air and passivation film on this surface side is lower than that of the semiconductor crystal, the electromagnetic field distribution of light is expanded toward the inside of the crystal, that is, the electromagnetic field will draw a long tail toward the GaAs substrate IO side, and since this GaAs substrate IO is not transparent to the laser beam, this laser beam will be
It is absorbed by the aAs substrate IO and becomes a loss. Therefore, in this embodiment, in order to avoid this, a GaAs substrate IO and three layers 3.2. and the high-resistance A11.1 which is transparent to laser light and electrically inert. G
The aAs layer 4 is provided. In this case, when the lower cladding layer l is a high resistance layer, it goes without saying that the same layer may be formed thickly.

In addition, in the above embodiment, in order to simplify the explanation, the case of a laser structure using an AfGaAs-based semiconductor material has been described, but the present invention is not necessarily limited to this case; for example, InP
Similar functions and effects can be obtained even in the case of a laser structure using other semiconductor materials such as a semiconductor material. and,
In the case of this InP-based laser structure, since the InP substrate itself is transparent to laser light, there is no need to provide a separate transparent region when a semi-insulating substrate is used.

Further, as the active layer, M is composed of multiple quantum wells.
It is not limited to a QW layer, but may be a single-layer quantum well, and as long as it is thin enough to be disordered by introducing impurities, even if the thickness is such that no quantum effect is necessarily observed. It can operate without any change in wood quality, and its thickness is usually less than 1000 Å. Furthermore, the composition of the cladding layer does not necessarily have to be uniform; for example, the well-known StlC (Sep.
arateConfinement l-1etero
structure) or GRIN (Gr
It is clear that the present invention can be similarly applied to structures such as ``aded Index''-SCI (structure, etc.).

〔Effect of the invention〕

As described in detail above, according to the present invention, the active layer is formed from both sides in the first . In a semiconductor laser device having a three-layer structure sandwiched between second cladding layers, a three-layer structure is formed on a region that is transparent to laser oscillation light formed on the substrate side, and the three-layer structure is In contrast, by selectively forming impurity regions of different conductivity types penetrating the active layer from the left and right sides, and increasing the conductivity of at least one cladding layer, a p-n junction is formed between the active region and the active region. 3, it is possible to provide a uniform carrier distribution in the active layer for efficient current injection, and to obtain a structure suitable for integration with electronic devices. Since the thickness up to the active layer in the layered structure is reduced, it has excellent features such as being able to easily form an impurity region that reaches the active layer by ion implantation and simplifying the manufacturing process.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing the general configuration of a semiconductor laser device to which an embodiment of the present invention is applied, and FIG.
FIG. 3 and FIG. 3 are sectional views each schematically showing the general structure of a conventional separate semiconductor laser device. l...p-+l GaAs cladding layer, 2...
MQW active layer, 3... n-A 11 GaAs cladding layer, 4... high resistance AuGaAs layer, 10---
- Semi-insulating (Sl) GaAs substrate, 20... p-type impurity ion implantation region, 21... n-type impurity ion implantation region. Figure 1 Figure 2 Attorney Masuo Oiwa Figure 3 Figure 2 Name of the invention Semiconductor laser device and its manufacturing method 3 Relationship with the case of the person making the amendment Patent applicant address 2-chome Marunouchi, Chiyoda-ku, Tokyo No. 2 No. 3 Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4 Subject of substituting amendment 6 Contents of amendment (1) The scope of claims in the specification will be amended as shown in the attached sheet. (2) “The guided mode...
And on this semi-insulating area, delete ". (3) Add the following sentence after "on the board side" on page 7, line 6 of the same book. “High resistance cutlet” (4) “Thick enough...” from page 7, line 20 to page 8, line 2 of the same book.
"On this semi-insulating region" is corrected to "a step of forming a sufficiently thick region of high resistance and transparent to laser oscillation light, and on this high resistance region." (5) "Clad layer 1" on page 13, lines 15-16 of the same book as "
cladding layer 3". (6) In the first line of page 14 of the same book, "it must be formed as soon as possible" is amended to "it is desirable to be formed." (7) "Clad layer 1" on page 14, line 19 of the same book is corrected to "clad layer 3." (8) Add the following sentence after "formed on the substrate side" on page 16, line 9 of the same book. "High resistance and" Claim (1) An active layer having a thickness of 100 OX or less or consisting of a single layer or multiple quantum wells, a cladding layer of a first conductivity type, and a first conductivity type cladding layer. A three-layer structure is provided between the second conductivity type or high-resistance cladding layer from both sides, and a first
．． and a semiconductor laser device characterized in that impurity regions of a second conductivity type are selectively formed from the left and right sides to disorder the corresponding regions of the active layer. (2) forming a region of high resistance that is sufficiently thick compared to the spread of the electromagnetic field distribution of the waveguide mode and transparent to the laser oscillation light; , or a single layer or multiple quantum wells, a cladding layer of a first conductivity type, and a first conductivity type cladding layer. A step of providing a three-layer structure with a thickness of 2 am or less sandwiched from both sides by second conductivity type or high-resistance cladding layers, Manufacturing a semiconductor laser device comprising at least the step of selectively forming impurity regions of a second conductivity type from the left and right sides by ion implantation to disorder the corresponding regions of the active layer. Method.

Claims (2)

[Claims] (1) An active layer with a thickness of 1000 Å or less, or consisting of a single layer or multiple quantum wells, is sandwiched from both sides by a cladding layer of a first conductivity type and a cladding layer of a first conductivity type, a second conductivity type, or a high resistance cladding layer. A three-layer structure is provided, and impurity regions of first and second conductivity types penetrating at least the active layer are selectively formed from the left and right sides of the three-layer structure, respectively, to form impurity regions of the corresponding active layer. A semiconductor laser device characterized by having a disordered region. (2) A step of forming a semi-insulating region that is sufficiently thick compared to the spread of the electromagnetic field distribution of the waveguide mode, and a step of forming a semi-insulating region with a thickness of 1000 Å or less, or a single layer or multiple layers on this semi-insulating region. A step of providing a three-layer structure with a thickness of 2 μm or less in which an active layer consisting of a quantum well is sandwiched from both sides by a cladding layer of a first conductivity type and a cladding layer of a first conductivity type, a second conductivity type, or a high resistance; selectively forming first and second conductivity type impurity regions penetrating at least the active layer in the three-layer structure by ion implantation from the left and right sides, respectively;
1. A method of manufacturing a semiconductor laser device, comprising at least the step of disordering a corresponding region of the active layer.