JPS59127891A - Manufacture of distributed feedback type semiconductor laser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention (1) is inspired by a method for manufacturing a distributed feedback semi-coupled laser that oscillates in a wave-like manner.

Due to advances in optical fibers and optical fibers, fiber communications have begun to be put to practical use. However, in 1E, which takes advantage of the characteristics of optical fiber communication, the main wall is a semiconductor laser that stably oscillates at a single wavelength. If a semiconductor laser, which cannot stably oscillate at a single wavelength, is used for optical 1m transmission, the transmission range will become narrow due to material dispersion of the optical fiber, and large noise will occur when the wave width changes. However, the signal-to-noise ratio of the transmission system deteriorates, resulting in poor transmission quality.
I invite people. For these reasons, distributed feedback semi-integral lasers have been studied with the aim of producing semiconductor lasers that oscillate at a single, stable wavelength. Distributed feedback type conductor lasers use a black reflector formed by unevenness provided near or in the active layer, whereas a normal semiconductor laser uses an open face of a crystal as a symmetry device. For this reason, a normal semiconductor laser tends to oscillate at multiple wavelengths, but a distributed-return type asteroid laser can only oscillate at a wavelength selected by the black reflector. However, in the conventional manufacturing method, after forming periodic irregularities by etching or etching, each layer structure including an active layer is immediately formed on the semiconductor layer. For this reason, the distributed plasma laser diode fabricated has an interstitial point as described below. This is because the drive current of the monodistribution feedback semiconductor laser is higher than that of a normal semiconductor laser, and its life is short. The reason why the drive current is high is that the irregularities existing near or in the active layer used as the flag reflector can only be formed shallowly, and therefore the reflectance of the flag reflector is low. Moreover, the reason why the lifetime is unknown is that the quality of the crystal formed on the uneven substrate is low and there are many crystal dislocations.

An object of the present invention is to provide a method for manufacturing a distributed feedback semiconductor laser that stably oscillates at a single wavelength and has characteristics of low driving current and long life.

In the manufacturing method of the present invention, first, the surface of semiconductor scrap VCJ#! A process of forming shallow linear irregularities by etching them in a gas to deepen them, and forming a structure containing an active layer on the semiconductor layer on which the deep irregularities are formed by epitaxial growth. The structure is such that the step of forming the wafer and the step of forming the wafer are performed continuously.

Next, the present invention will be explained using the drawings. Figure 1 is a diagram illustrating a -'st elliptical example of the present invention, in which one culm is formed by etching and etching p'i w-shaped unevenness in a gas, and a semiconductor layer is epitaxially grown on the unevenness. FIG. FIG. 2 is a process diagram showing an outline of the process of the present invention.

Linear concavo-convex shapes are usually formed on semi-barrel substrates, as shown in FIG. 2 (,). It is written using a photolithography method using laser interference φ of 4:11. In this embodiment, an n-type InP substrate 22 is used as the semiconductor substrate.

AZ-1350 was used as the photoresist 21, and a laser F nihelium cadmium laser was used. Then, the InP% covered by the photoresist 21 removed periodically is
By etching the plate 22 with chrome methanol, a circular recess 23 is formed. In the conventional manufacturing method, the semiconductor t +
I! Although the i-contact epitaxial emission was performed, the reflectance of the flag reflector was low because the unevenness was shallow, which caused the drive current to increase. In addition, the process of etching with bromo-methanol was a chemical air cleaning process and was a separate process from the formation process, so the uneven surface of the InP semiconductor was easily oxidized, the quality of the crystal in the epitaxially grown layer was poor, and dislocations were caused. It occurs in large quantities in the growth layer, causing a shortened lifespan. In this example, an InP substrate having shallowly formed irregularities is placed in the substrate holder 16KInP substrate 22 in the reactor 15 shown in FIG. 1, and etched with hydrogen chloride gas. ,700
When the substrate was exposed to 1% hydrogen chloride gas for 20 seconds at a substrate temperature of .degree. C., deep irregularities as shown in FIG. 2(b) K were obtained. Furthermore, 25 in FIG. 1 was obtained by feeding HCI gas to the In melt 12 in FIG. 1 to cause a reaction, and feeding H, 8 gas to the capillary tube 111CPH4. Non-doped InGaAsP26,I
HC1 gas was sent to the n-mel) 12 and Ga melt 13 to cause a reaction, and PH, A, H, and gases were sent to the thin tube 11.

f) InP layer 27 was written in the same manner except that ZN gas was supplied as a P dopant. In this example, since gas etching is performed using HCI, the (111)5-plane of the crystal is selectively etched, nang, '! ,,Deep unevenness as shown in Fig. 2 (bl) was obtained.In addition, since epitaxial bv i+ is performed continuously after machining and ching, I,
A good epitaxial growth layer was obtained without #f change on the surface of the P substrate. As a result, the number of dislocation clouds contained in the growth layer was reduced, and shortening of the lifespan was prevented. Therefore 1
According to the present invention, the driving current is low.

A method for shielding a distributed feedback semiconductor laser that has a long lifetime and stably oscillates at a single wavelength can be obtained.

In the above example, the In0aAsP/IIP system was used.

This family has not been determined, and GaA IAs/(
iaAs.

InGaAsP/GaAs, InGaA IP
It is clear that materials such as /GaAs may also be used.

In the above-mentioned method 1, the shallow 11!1 convexity is formed by the IJ Sogera-Fie method.

[Brief explanation of drawings]

Figure 1 t-4 ¥, a rounding device for purchasing light, 1
1 is a thin tube, 12 uln melt, 13 pieces (31//l
z6-to, 15Fi reaction tube, 16 is a substrate holder. FIG. 2 is a schematic diagram showing the manufacturing process of the present invention, and shows changes in the cross-sectional shape of the wafer in each process. (,) shows a wafer with shallow irregularities obtained by photolithography, (b) shows a wafer with sharp irregularities etched in gas, and (c) shows the cross-sectional shape of the wafer after epitaxial growth. 7 photoresist, 23 shallow concave surface, 22 InP substrate, 24 deep uneven surface, 25 n-InP cladding layer, 26 non-doped I
nGaAsP active layer, 27 indicates p-InP cladding layer. IU

Claims (1)

[Claims] The unevenness is the shape of the MJ period9. In the method of manufacturing a distributed feedback type semi-structured laser by forming a multilayer structure containing an active layer f on the half-structured 8-layer structure, the shallow irregularities formed in the roughness are etched and chimed in air. A method for manufacturing a distributed feedback semi-integral laser, comprising the steps of: successively performing a step of making it sparse, and a step of epitaxially growing a semi-ψ body on the deep i-convex surface.