JPS59231885A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To flow all injected currents through an active layer, and to obtain an optical semiconductor device having high reliability and long life by laminating a semiconductor layer containing the active layer on a semiconductor substrate, growing the semiconductor layer in an epitaxial manner in a liquid phase, mesa- etching the grown layer and previously coating the interface of the grown layer with an insulating protective film. CONSTITUTION:An N type InP light guide layer 15, an N type or P type InGaAsP active layer 16, a P type InP light guide layer 17, and a P type InGaAsP cap layer 18 are laminated on an N type InP substrate 14, and grown in an epitaxial manner in a liquid phase. A striped protective film 19 consisting a of SiO2 or Al2O3 or the like in predetermined size is formed on the layer 18, and laminate is mesa-etched until etching intrudes to the layer 15 by using 1% bromine methanol while employing the protective film as a mask. The film 19 is removed, the whole exposed surface is coated with a protective film 20 composed of SiO2, Al2O3 or the like extending over the upper section of the layer 15 from a mesa section, and the upper section of the layer 18 is removed and a P<+> type diffusion region 21 for ohmic contact intruding into the layer 17 is formed in the removed section.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an optical semiconductor device, and in particular to an optical semiconductor device in which all injected current flows through an active layer, thereby achieving a long life and high reliability. It is related to the device.

[Background of the invention]

Embedded optical semiconductor devices have a small oscillation threshold current and are easy to control in transverse mode, and are particularly promising as light sources for optical communications.

Conventionally, the structure of this type of optical semiconductor device is as shown in FIG. 1, and it is generally manufactured as follows. That is, an n-type semiconductor substrate 1'' and an n-type semiconductor optical guide layer 2 are provided.
After sequentially forming an n-type or p-type semiconductor active layer 3, an n-type semiconductor light guide layer 4, and a p-type semiconductor cap layer 5 made of the same material as the n-type or p-type semiconductor active layer 3, ,
5i having a predetermined width on the surface of the p-type semiconductor cap layer 5
A stripe-shaped protective film made of 02 film or A1.203 film is provided, and the portion other than the protective film is removed by etching until a part of the n-type semiconductor optical kite layer 2 is reached. next,
An n-type semiconductor optical guide layer 2 is placed on the etched portion.
A p-type semiconductor buried layer 6 and an n-type semiconductor buried layer 7 made of the same material as the n-type semiconductor active layer 3 and an n-type semiconductor cap layer 8 made of the same material as the n-type or p-type semiconductor active layer 3 were formed, and the protective film was removed. After that, a protective layer 9 made of a 5i02 film or an At203 film having an opening wider than the stripe width is formed.
A p-type semiconductor cap layer 8 is provided with a p-type diffusion layer 10 having a depth of reaching a part of the p-type semiconductor light guide layer 4 through the opening, and an electrode 11 is provided thereon.

However, in the conventional technology mentioned in 1, there is an etching process between the two crystal growths, so the part formed by the first stage crystal growth and the part formed by the second stage crystal growth. The interface 1-ζ with mesa interface 1
2, there are many defect levels or their origins. These defects multiply with the operation of the embedded optical semiconductor device, and the leakage current component of the path indicated by the reference numeral 13 in FIG. The flow component decreases. This has the drawback of causing deterioration such as an increase in the oscillation threshold current and a decrease in external quantum efficiency, and even leading to a fatal failure in which laser oscillation stops.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the prior art mentioned in 1.
It is an object of the present invention to provide an optical semiconductor device having a long life and high reliability without any leakage current component that does not pass through an active layer.

[Summary of the invention]

The main point of the present invention is to form a structure in which an insulating protective film is directly formed on the mesa interface formed by mesa etching the portion formed in the first stage of crystal growth. The membrane allows all of the injected current to flow through the active layer, eliminating leakage current components that flow through parts other than the active layer, which is a drawback of the prior art.

[Embodiments of the invention]

Hereinafter, one embodiment of the optical semiconductor device according to the present invention will be described.
The case will be explained using the drawings as an example.

2 to 6 are explanatory diagrams of the manufacturing process of the optical semiconductor device of this embodiment. First, as shown in Figure 2, n-type 1n
An n-type InP light guide layer 15, an n-type or p-type InGaAsP active layer 16, a p-type InP light guide layer 17, and a p-type InGaAsP cap layer 18 are grown on a P substrate 14 by liquid phase epitaxial growth. are used to stack them continuously. Next, as shown in Fig. 3, p-type 1nGaAsP
5i having a width of 5 to 6 μm in the cap layer 18,1-
A stripe-shaped protective film 19 made of 02 film or At203 film is formed, and the area 1 other than the part covered by the protective film 19 is coated with n-type I using a 1% solution of bromine methanol.
Etching is performed to a depth that reaches a part of the nP optical guide layer 15. Subsequently, after removing the protective film 19, as shown in FIG.
A film with a thickness of 0.1 to 1 μm is deposited on the nGaAsP cap layer 18'' by an ion blasting method, a CVD method, etc.
An insulating protective film 2o made of an i02 film or an At203 film is formed. Next, as shown in FIG.
After forming a stripe-shaped window on the p-type InGaAsP cap layer 18, Zn is vapor-phase diffused through the stripe-shaped window, and the pI diffusion layer 21 for ohmic contact is formed with a p-type 1nP optical kit. It is formed to a depth that reaches a portion of layer 17. Thereafter, as shown in FIG. 6, electrodes 22 are formed on the surface of the protective film 2o including the p+ diffusion layer 21, and on the back surface of the n-type InP substrate 14, thereby completing an optical semiconductor device.

-1- According to the structure described, by providing the insulating protective film 2o, all the injected current is n-type or p-type 1nG.
Since it passes through the aASP active layer 1G, there is no leakage current component, which was a drawback of the prior art, and a long-life optical semiconductor device can be realized. In addition, the stabilization of the transverse moat is achieved by the active layer width W (6th
(as shown in the figure), it is possible to obtain the same performance as a conventional embedded optical semiconductor device.

In the above embodiment, the case of InP was explained, but similar effects can be obtained with other compound semiconductors, such as GaAs.

〔Effect of the invention〕

According to the present invention, an optical semiconductor device has a structure in which an insulating protective film is directly formed on the mesa interface, so that the current injected into the optical semiconductor device entirely flows through the active layer. Since the leakage current component is negligible, an optical semiconductor device having a long life and high reliability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional embedded optical semiconductor device, and FIGS. 2 to 6 are explanatory diagrams of the manufacturing process of an embodiment of the optical semiconductor device according to the present invention. Explanation of symbols 14...N-type 1nP substrate 15...N-type InP light guide layer 16-n-type or p-type 1nGaAsP active layer 17...p-type 1nP optical kite layer 18-p-type InGaAsP key 1" bubble layer 19...
・Protective film 20... Insulating protective film 21...
p4-diffusion layer 22... Electrode agent patent attorney
Junnosuke Nakamura 11 illustrations 2 illustrations 3 areas 4 illustrations 5

Claims (1)

[Claims] An n-type semiconductor light guide layer, an n-type or p-type semiconductor active layer, an n-type semiconductor light guide layer, and an n-type semiconductor light guide layer on an n-type semiconductor substrate.
After sequentially forming a type or p-type semiconductor cap layer with a width required for the active layer, the n-type semiconductor light is passed through a striped protective film provided on the n-type or p-type semiconductor cap layer. Mesa etching is performed to a part of the guide layer, the central part of the striped protective film is removed to create an opening, and the n-type semiconductor light guide passes through the n-type or p-type semiconductor cap layer from the opening. An optical semiconductor device in which a dopant is diffused to a depth that reaches a part of the layer, and then electrodes are provided on the surface of the diffusion layer and the back surface of the n-type semiconductor substrate, the mesa interface produced by the mesa etching. An optical semiconductor device characterized in that an insulating protective film is formed on.