JPS6249687A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To reduce a parasitic capacity and a leakage current by a method wherein a buried layer of semiconductor layer is formed of a material made of polyimide resin mixed with another material with refractive index different from that of polyimide resin. CONSTITUTION:An n-InP clad layer 12, an InGaAsP active layer 13, a p-InP clad layer 14 and a p-InGaAsP contact layer 15 are laiminated on an n-InP substrate 11. Next, a material made of polyimide mixed with InP powder is buried to form a buried layer 16. The preferable material to be mixed with polyimide is InP or GaAs with mixing ration of around 1:1-1:5. Finally a p- electrode 17 and an n-electrode 18 are formed respectively on upper and lower surface of formed laser.

Description

[Detailed Description of the Invention] [Summary] The present invention is a buried semiconductor laser made of a laminated layer of a compound containing indium phosphide. This creates a layer that increases parasitic capacitance, which limits the high-speed operation of semiconductor lasers.To solve this problem, the material of the buried layer is made of high-resistance polyimide as the main component, and indium phosphorus is added to the material of the buried layer. By mixing a material with a high refractive index to approximate the above, a buried layer with high insulation properties and effective for light confinement is formed.

[Industrial Field of Application] The present invention relates to a buried semiconductor laser, and more particularly to a material for a buried layer.

In recent years, semiconductor lasers have been widely used as light emitting elements in optical communication systems, and are being improved and developed as elements of new communication technology for the information society.

Semiconductor lasers have various structures, but the most typical structure is a buried heterostructure semiconductor laser, and the buried layer structure is usually a p-n junction indium phosphide (Indium phosphorus).
Since it is composed of P), it has a certain degree of conductivity, and when a voltage is applied to that region, a depletion layer is created at the p-n junction, resulting in an increase in electrical capacitance, resulting in an increase in parasitic capacitance. This limits the high-speed operation of the semiconductor laser, and there is a demand for improvement.

[Prior Art] FIG. 4 is a schematic cross-sectional view of a main part of a conventional buried type heterostructure semiconductor laser.

There is an n-1nP substrate 1, and n-InP is sequentially deposited on its surface.
cladding layer 2, active layer 3 of indium, gallium arsenide phosphide (InGaAsP) that emits laser light, p-InP
A cladding layer 4 of p-InGaAsP, a contact layer 5 of p-InGaAsP, and an n-rnP layer 6 as a buried layer, a p-1nP layer 6.
There is a bonding layer with layer 7, and a p-electrode 8 and an n-electrode 9 are provided as electrodes on the upper and lower surfaces of the semiconductor laser.

In order to operate the semiconductor laser having the above structure, the p-electrode 8
When a voltage is applied between the n-electrode 9 and the n-electrode 9, a depletion layer is formed at the junction between the n-1nP layer 6 and the p-InP layer 7 of the buried layer due to the electric field, which increases the capacitance of the buried layer. .

Furthermore, the current that originally flows in the active layer 3 passes through the pInGaAsP contact layer 5 and the p-1nP ground layer 4, but instead flows in the direction of the buried layer, causing a leakage current to flow as shown by the arrow, which reduces luminous efficiency. become.

For the above reasons, conventional embedded semiconductor lasers have a decrease in luminous efficiency and are limited in high-speed modulation, and are limited to high-speed modulation of approximately several hundred Mb/sec, which is less than the desired 1Gb. A shortcoming is that high-speed modulation of about /sec or higher cannot be achieved with conventional semiconductor lasers.

[Problems to be Solved by the Invention] A problem with conventional buried-type semiconductor lasers is that high-speed modulation of the semiconductor laser is limited due to the parasitic capacitance of the buried layer.

[Means for Solving the Problems] The present invention provides a semiconductor laser for solving the above-mentioned problems. In the semiconductor laser of The present invention provides a semiconductor laser in which a buried layer is made of a polyimide resin mixed with a substance having a high optical refractive index.

[Function] The present invention provides a buried layer of a buried semiconductor laser,
This design takes into account embedded semiconductor lasers that use high insulators and do not increase parasitic capacitance even during operation.
Polyimide resin is the most suitable material, and In
Efforts have been made, such as selecting a mixed material to approximate the optical refractive index of P. This prevents an increase in parasitic capacitance and leakage current, making it possible to create an embedded type that can perform high-speed modulation. This led to the creation of semiconductor lasers.

[Example] FIGS. 1(a) to 1(C) are schematic cross-sectional views of main parts for explaining the method of manufacturing an embedded semiconductor laser of the present invention.

In FIG. 1(a), n-
A cladding layer 12 of InP, an active layer 13 of indium, gallium arsenide phosphide (rnGaAsP), a craft layer 14 of p-InP, and a contact layer 15 of p-1nGaAsP are laminated and mesa etched.

In FIG. 1(b), a material made of a mixture of polyimide and InP powder is embedded as the buried layer 16. Polyimide is a perfect insulator, but since its refractive index is quite different from InP, it is preferable to use InP as much as possible. In order to approximate the refractive index of the polyimide, the material to be mixed with polyimide is InP or Ga
A s is the most desirable, and the mixing ratio is approximately 1:1 ~
This can be achieved by setting the ratio to about 1:5.

The embedding method is to melt these mixed materials with thinner, embed them with a spinner, and then dry them at a temperature of 150° C. or higher.

FIG. 1C shows a completed semiconductor laser by forming a p-electrode 17 and an n-electrode 18 on the upper and lower surfaces of the formed semiconductor laser.

In the buried heterostructure semiconductor laser of the present invention, the buried layer has a resistance of 108 to 1011 Ωcn+, which is significantly larger than the conventional resistance value of several tens of Ωcm to 100 kΩcm. The capacitance of the layer is 10 pF to 20 pF, which is lower than the capacitance of the buried layer of the conventional structure, which is 80 to 100 pF.

FIG. 2 is a sectional view showing another embodiment using the embedding material of the present invention.

There is an n-1nP substrate 21, and n-In is sequentially deposited on its surface.
P cladding layer 22, InGaAsP active layer 23, p
A cladding layer 24 of -InP and a contact layer 25 of p -1nGaAsP are laminated and mesa etched.
An electrode 26 and an n-electrode 27 are formed, and in this structure, a current confinement layer 28 is provided, and the current confinement layer is made of a dielectric film such as silicon dioxide or a semiconductor 19! such as InP! (Polycrystal or single crystal may be used).

Even in this case, the material mixed with polyimide and InP or GaAs powder can be buried in the buried layer 29 in the same manner as described above.

FIG. 3 is a cross-sectional view of a semiconductor laser having a structure in which a p-electrode and an n-electrode are provided in the same direction.

There is an InP substrate 31, and on its surface there is a cladding layer 32 of n-InP and an active layer of InGaAsP. 33, p-rn
A P cladding layer 34 and a p-IrIGaAsP contact layer 35 are laminated and mesa etched to form a p-electrode 3.
6 and n-electrode 37 are formed, but the buried Fi
As i3B, the polyimide of the present invention and InP or Ga
A semiconductor laser can be formed by embedding a material mixed with As powder.

[Effects of the Invention] As described above in detail, the buried semiconductor laser according to the present invention has great effects in that it can significantly reduce parasitic capacitance and leakage current, and can be used for high-speed modulation.

[Brief explanation of the drawing]

1(a) to 1(C) are schematic cross-sectional views of main parts for explaining the manufacturing method of the embedded semiconductor laser of the present invention, and FIG. 2 is another embodiment using the embedding material of the present invention. It is a sectional view showing an example. FIG. 3 is a cross-sectional view of a semiconductor laser having a structure in which a p-electrode and an n-electrode are provided in the same direction according to the present invention. FIG. 4 is a schematic cross-sectional view of a main part of a conventional buried-type heterostructure semiconductor laser. , 11 is an n-1nP substrate, 12 is a cladding layer, 13 is an active layer, 14 is a cladding layer, 15 is a contact layer, 16 is a buried layer, 17 is a p-electrode,
Reference numeral 18 indicates an n-electrode. CG) (b) (C) Invention 1 is erupted L-ㅅㅈ袈上 4T Reiyu end tear 1st figure falcon invention L is guided - the 1st pier 11rg 2nd figure Douen lightening Destruction is the original 7 trace m Figure 3 Figure 4

Claims (1)

[Claims] In a buried semiconductor laser made of a laminated layer of a compound containing indium phosphorus, the buried layer (16) of the semiconductor laser is made of a material made of a polyimide resin mixed with a substance having a different optical refractive index from the polyimide resin. A semiconductor laser characterized in that the buried layer (16) described above is formed.