JPH0548206A - Inp laser diode and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an InP laser diode having a current constricting layer, which blocks currents surely, and provide the easy manufacturing method thereof, which excels in its reproducibility, uniformity and controllability. CONSTITUTION:By implanting ions in an InP substrate 1 to a predetermined depth, and by annealing the substrate, a current constricting layer 2 is formed. Then, an active layer 5 sandwiched between clad layers is formed in the location, which exists in a groove 6 formed so as to reach a place deeper than the current constricting layer 2, and which exists concurrently in the current constricting layer 2 too.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an InP laser diode and a method for manufacturing the same. More specifically, 1.3 μm, which is a low wavelength dispersion region in the field of optical fiber communication.
It is used for laser diodes in the band and the 1.55 μm band, which is an extremely low loss region.

[0002]

2. Description of the Related Art A semiconductor laser diode can be made compact and lightweight, and its oscillation wavelength can be selected in a wide range. In particular, a so-called double hetero structure in which both sides of a semiconductor serving as a medium of a laser are sandwiched by semiconductors having a higher band energy and a smaller refractive index is effective. Conventionally, there is a semiconductor laser diode, for example, an InP laser diode or the like, a current block layer (pnp or npn) is formed on an InP substrate, and a V-shaped or deeper than the current block layer is formed to reach the InP substrate. It has a structure in which an active layer for laser oscillation is laminated in an arrow head type groove.

A method for obtaining the above InP laser diode will be described below. That is, a current block layer is formed on an InP substrate by a liquid phase epitaxial growth method, and then a V-shaped or arrowhead-shaped groove is formed at a depth reaching the InP substrate deeper than the current block layer by chemical etching. After that, the active layer for laser oscillation is embedded in the groove again by the liquid phase epitaxial growth method.

[0004]

By the way, in the prior art, the liquid phase epitaxial growth method must be used twice as described above. This liquid phase epitaxial growth method forms the basis of semiconductor laser fabrication technology, in which the substrate, solvent, and added impurities are kept at a high temperature in a hydrogen atmosphere in a quartz tube, mixed well, and then gradually cooled by a predetermined temperature program. In order to obtain the desired composition, strict temperature control and accumulation of advanced manufacturing technology were necessary.

In the semiconductor laser diode thus obtained, a laminated structure of pnp or npn is formed by the first liquid phase epitaxial growth, and the reverse junction diode blocks the current. However, as described above, When the liquid phase epitaxial growth method is used, a semiconductor laser diode having a satisfactory block performance cannot be obtained due to the difficulties involved.

The laminated structure of the semiconductor laser diode thus obtained is a parasitic thyristor structure. Therefore, when the laser oscillation current is increased, there is a problem that the current block cannot be performed due to the trigger of the parasitic thyristor. The present invention has been made to solve the above problems, provides a semiconductor laser diode with good performance without the thyristor trigger phenomenon, and in manufacturing the semiconductor laser diode, the manufacturing is easy, and the productivity and the yield are high. It aims at providing the manufacturing method which improves.

[0007]

In order to achieve the above object, the InP laser diode of the present invention (hereinafter referred to as the first invention) according to claim 1 is a first conductivity type InP laser diode.
At a predetermined depth in the substrate, an ion-implanted layer of a substance that forms an insulator by bonding with the substrate material is formed, and a groove reaching a position deeper than the ion-implanted layer is formed. A first conductivity type InP clad layer is formed,
An active layer is formed on the clad layer, a second conductivity type clad layer is formed on the upper surface of the substrate including the active layer, and the ion-implanted layer constitutes a current constriction layer. Attached.

The present invention corresponding to claim 2 (hereinafter,
In the method for manufacturing an InP laser diode according to the second invention), the current confinement layer is formed by performing the following step (a) or (b), then an oxide film is formed on the substrate, and then the A groove reaching a position deeper than the current confinement layer is formed by opening a predetermined portion of the oxide film and then etching, and then a first conductivity type InP clad layer is formed in the groove and then the first conductivity type is formed. It is characterized by forming an active layer on the InP clad layer and then forming a second conductivity type InP clad layer on the active layer and on the oxide film. (A) A step of implanting ions of a substance that combines with the material of the first conductivity type InP substrate to form an insulator and then anneals the substrate. (B) A step of annealing the first conductivity type InP substrate while implanting ions of a substance that binds to the material of the substrate and forms an insulator to a predetermined depth.

[0009]

With the ion implantation method, it is possible to implant ions into the layer from the substrate surface to a desired depth almost uniformly by changing the energy of the implanted ions.
Therefore, by performing ion implantation by such a method, for example, as shown in FIG. 1, a high-resistance buried layer, that is, a current confinement layer is formed at a position where the depth D from the surface of the substrate is several μm. can do.

In addition, the current confinement layer thus formed by the ion implantation method blocks the current and does not cause the leakage of current due to the pnp or npn structure.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of an embodiment of the first invention. A current confinement layer 2 having an implantation depth D of several μm is formed from the surface of the n-InP substrate 1. Further, a predetermined portion of the silicon oxide film 3 formed on the surface of the n-InP substrate 1 is opened, and a V-shaped groove 6 reaching a position deeper than the current confinement layer 2 is formed. InP clad layer 4a
And a crescent-shaped InGaAsP active layer 5 is formed on the n-InP clad layer 4a.
A p-InP clad layer 4b is formed over the silicon oxide film 3 and above. Further, a p electrode and an n electrode are formed on the upper surface and the lower surface of the substrate having such a structure, respectively. The current confinement layer 2 is formed by ion implantation and annealing, which will be described later, and is formed to a desired depth and uniformly, and is an insulating layer that blocks current and has high blocking performance. Therefore, even when the laser oscillation current is increased, the current can be blocked without causing the thyristor trigger phenomenon.

A method of manufacturing an InP laser diode having the above-described structure and operation will be described below with reference to the drawings. FIG. 2 is a schematic sectional view for explaining an embodiment of the second invention over time. First, the n-InP substrate 1 to be used
By implanting nitrogen ions in the plane orientation of the (100) plane, the implantation layer 2a is formed in the portion under the substrate where the depth D = several μm. The depth D of several μm is a depth necessary for forming a laser structure of the device, and the energy of nitrogen ions at this time is in the MeV order [FIG.
(A)].

Next, the n-InP substrate 1 is annealed at 500 to 600 ° C. in a hydrogen atmosphere. By this treatment, the implantation layer 2a becomes a high resistance insulating layer, and the current confinement layer 2 is formed. The current confinement layer 2 is hardly altered by the subsequent thermal history [FIG. 2 (b)]. For the experimental basis of the above-mentioned steps, see, for example, F.Xiong. Et al Ma-t. Res.Soc.Symp.Proc.Vol, (198
8), pp105-111, and is publicly known.

Next, a silicon oxide film 3 is formed on the n-InP substrate 1, and then a silicon oxide film is formed by resist photolithography with respect to the plane orientation of the (011) plane of the n-InP substrate 1. 3 stripe window pattern is formed [FIG. 2 (c)]. And this n-InP
The window portion of the substrate 1 is chemically etched using an etching solution of HCl / H ₃ PO ₄ . At this time, the V-shaped groove 6 is formed due to the difference in the etching rate of the InP crystal plane. The groove 6 is formed so as to reach a position deeper than the current confinement layer 2. The experimental basis for forming the V-shaped groove 6 is described in, for example, Suematsu et al., Semiconductor and Optical Integrated Circuits, pp. 429-432, Ohmsha, Ltd., and is known [FIG. 2 (d)]. ..

Further, an n-InP clad layer 4a is formed in the V-shaped groove 6 by a liquid phase epitaxial growth method,
A crescent-shaped InGaAsP active layer 5 is formed on the n-InP clad layer 4a, and a p-InP clad layer 4b is sequentially formed on the InGaAsP active layer 5 and the silicon oxide film 3 [FIG. 2 (e)]. .. Finally, a desired InP laser diode is obtained by forming the p electrode 7b and the n electrode 7a on the upper surface and the lower surface of the n-InP substrate 1, respectively, by vapor deposition or the like (FIG. 1).

In the manufacturing method described above, annealing is performed after ion implantation into the InP substrate, but as another method, the temperature of the InP substrate may be raised and heat treatment may be performed while ion implantation is performed. Further, the implanted ions are not limited to nitrogen ions, but may be other ions that combine with the material of the InP substrate to form an insulator.

[0017]

As described above, according to the present invention, when forming the current confinement layer, it is necessary to perform the liquid phase epitaxial growth method, which requires a sophisticated manufacturing technique such as temperature control, as in the conventional case. Instead, by performing ion implantation and annealing on the substrate instead, a manufacturing method excellent in reproducibility, uniformity, and controllability can be realized. As a result, the productivity of the InP laser diode is improved, and
The yield is also improved. Further, it is difficult to increase the area by the liquid phase epitaxial growth method, for example, the limit is about 20 mm × 20 mm, but in the process of ion implantation and annealing, it is possible to perform with a large area, for example, 50 mmφ, so this manufacturing process In this way, batch processing can be performed, and the manufacturing cost can be reduced.

Further, In obtained by the manufacturing method of the present invention
In the P laser diode, the current is reliably blocked in the current confinement layer, and the current does not leak. Therefore, an element with improved performance can be provided by a simple manufacturing method.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of the first invention.

FIG. 2 is an explanatory diagram of an embodiment of the second invention.

[Explanation of symbols]

 1 ... n-InP substrate 2 ... current confinement layer 4a ... n-InP cladding layer 4b ... p-InP cladding layer 5 ... InGaAsP active layer 6 ... groove

Claims (2)

[Claims] 1. A predetermined depth in an InP substrate of the first conductivity type,
An ion-implanted layer of a substance that forms an insulator by bonding with the substrate material is formed, and a groove reaching a position deeper than the ion-implanted layer is formed.
A conductive type InP clad layer is formed, an active layer is formed on the clad layer, a second conductive type clad layer is formed on the upper surface of the substrate including the active layer, and the ion implantation layer is a current confinement layer. InP laser diode composed of layers. 2. A current confinement layer is formed by performing the following step (a) or (b), an oxide film is formed on the substrate, and then a predetermined portion of the oxide film is opened.
Then, etching is performed to form a groove reaching a position deeper than the current confinement layer, and then a first conductivity type InP clad layer is formed in the groove, and then an active layer is formed on the first conductivity type InP clad layer. And then forming a second conductivity type InP clad layer on the active layer and on the oxide film. (A) A step of implanting ions of a substance that combines with the material of the first conductivity type InP substrate to form an insulator and then anneals the substrate. (B) A step of annealing the first conductivity type InP substrate while implanting ions of a substance that binds to the material of the substrate and forms an insulator to a predetermined depth.