JPH02285692A - Manufacture of semiconductor light source - 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 [Industrial Application Field 1] The present invention relates to a method for manufacturing an integrated wavelength tunable light source made of a compound semiconductor, which is applicable to the field of optical integrated circuits or optoelectronic integrated circuits.

[Prior Art] Conventionally, attempts have been made to convert the wavelength of laser light into another wavelength by introducing laser light into a nonlinear optical crystal and using the nonlinear optical effect to excite optical parameters.・Electronics (Optical
electronics) J [Author Yarif (
Amnon Yariv)] [Publisher: Holt 5anders Japan
Pan) ] (3rd edition), P., 252-263, etc., and a light source for analyzers that combines a YAG laser and a lithium niobate single crystal has been put into practical use. .

FIG. 2 shows a schematic configuration diagram. Part A is the laser oscillation part,
Part B shows an optical parametric excitation section.

[Problems to be Solved by the Invention] However, the system configured by combining the plurality of individual elements described above has the following problems.

1. Since each element is modularized, it does not become a constituent element of an optoelectronic integrated circuit.

2. Since extremely high-quality single crystals are required, costs for crystal growth, crystal polishing, assembly, etc. are high.

3. It is also difficult to align the optical axis of the optical system.

4 Therefore, energy conversion efficiency is low.

An object of the present invention is to solve the above problems and provide a device that can be integrated with Brenna.

[Means for Solving the Problems] In order to solve the problems described above, the present invention is characterized by comprising the following means.

1. The crystal for optical parametric excitation is a compound semiconductor crystal.

2. The light source is a semiconductor laser.

3. The compound semiconductor is formed by selective epitaxial growth on a substrate common to the semiconductor laser.

4. The optical parametric excitation section forms an optical waveguide and is optically coupled to the laser oscillation section optical waveguide.

5. The optical coupling is based on the same principle as an optical directional coupler.

[Example] An example of the present invention will be described below. The basic idea of the present invention is to use laser light from a well-known semiconductor laser as a light source and optically couple it to optical waveguides made of nonlinear optical crystals arranged adjacent to both sides of a laser resonator.
After generating optical parametric oscillation using three optical waveguides, that is, a laser optical waveguide and the two optical waveguides, the wavelength-converted light is extracted from one or both of the end faces of the optical waveguides on both sides. be. At this time, the angular frequency W of the laser beam
3. Between the angular frequencies W1 and W2 of the light induced in the two optical waveguides on both sides, there is a difference W s ” due to parametric excitation.
It is set so that the relationship W + + W 2 holds true. To control W and W2, a method is adopted in which an appropriate voltage is applied to the optical waveguide and the refractive index of the crystal is varied by the electro-optic effect. Thereby, for example, Wl can be varied continuously while maintaining the above relational expression.

FIG. 1 is a schematic diagram of the structure of a device showing one embodiment of the present invention. (a) is a schematic cross-sectional view, and (b) is a schematic plan view.

Here, a method for manufacturing this structure will be described. First, a central laser oscillation part is formed. On an n-type GaAs substrate,
An n-type GaAs buffer layer 150 is deposited. Sequential n A
lx Ga+-x As (x=0.1) 102
, n-Ga As l 03, P Alx Ga+-x
As (x = 01) 104, P-Ga As l
51 and are epitaxially grown and stacked by MOCVD. Layer 102 is a laser oscillation active layer. next,
Etch and remove both sides leaving the laser resonator part.
The surface of the buffer layer 150 is removed. Next, the surface other than the optical waveguide portions 119 and 120 on both sides of the laser resonator is
i Coat with O□ film. Next, in the 119 and 120 portions, a Zn Sx Se layer as a cladding layer - x l O
7,111 is formed by selective epitaxial growth using the MOCVD method. Continuing, the leading wave layer 108
, 112 are similarly formed by selective evixaxial growth. In this manner, three optical waveguide layers 102, 108, 1]2 are formed adjacent to each other on the same plane.

The conditions for the MOCVD evixial growth are as follows.

(1) Laser resonator partial raw material gas: Trimethylgallium/trimethylaluminum, arsine Substrate temperature: 00° to 820°C Pressure: 700 to 790 Torr Growth rate:
0.07 to 0.08 um/min (2) ZnSe optical waveguide part raw material gas: Trimethyl zinc, hydrogen sulfide, hydrogen selenide Substrate temperature = 250° to 350°C Pressure Crab 100 Torr or less Growth rate: 005 to 007 μm/min Here Now, the method for manufacturing the optical waveguide section will be described in more detail. FIG. 3 is a diagram explaining the process, showing the cross-sectional structure of the thin film crystal. After forming the semiconductor laser structure, the hatched portion 303 is etched away leaving the laser oscillation portion 301. The n-type GaAs buffer layer 150 in FIG. 1 is removed.

The exposed n-GaAs substrate 300 becomes an epitaxial substrate for other optical waveguide forming films. The etching is EC
Using the RIBE method using an R-type plasma device. The etching gas is a mixed gas of Ar/CCl4. The flow rates and pressures of both gases are set so that the etched surface becomes a mirror surface. In the RIBE process, the surface is smoother and some corners are formed to be very close to right angles, compared to the normal scientific edging process. Therefore, it is of high quality as an erectile surface. Next, the surface other than the portion 306 where the intended optical waveguide will be erectically grown is protected with a silicon oxide 5iOz film 304. First, silicon oxide SiO□ 304 is deposited on the entire surface by thermal CVD or the like. An additional layer of SiO□ 305 is deposited on areas other than the optical waveguide and laser oscillator portion. Next, vacuuming is performed using photolithography, and the SiO□ at the 306 portion is removed by etching to expose the epitaxial growth surface. Next, 20Sx 5el
-x layer, then evixaxially grow two layers in the order of zinc selenide (ZnSe). This is carried out using the MOCVD method, and the important point is that by selecting the epitaxial growth conditions, conditions are set so that epitaxial growth occurs on the n GaAs surface 305 but no deposition occurs on the surface of the SiO□ film 304 and 305. It is possible. this is,
Both a ZnS film and a ZnSe film can be used, and can be selectively epitaxially grown to form the optical waveguide section 307. The Zn Sx Se layer-x layer serves as an optical waveguide cladding layer and a buffer layer that alleviates mismatching of lattice constants between the Zn Se crystal and the Ga As crystal. 302 is an active layer which is a laser beam oscillation region;
08 is another optical waveguide layer, namely a ZnSe layer. Part 307 is epitaxially grown so that both (302, 308) form the same plane. In this way, the lasing region, ie, the active layer, can be formed on one or both sides of the lasing region, which is another optical waveguide that is laterally optically coupled. The above-mentioned erectile growth uses Z as a raw material.
Using organic compounds of n, S and Se, the growth pressure was 10
0 Torr or less, growth temperature 700° to 820°C, V
This is carried out by a reduced pressure MOCVD method under conditions where the molar ratio of Group I raw materials to Group II raw materials is 6 or less.

Furthermore, as a method, an epitaxial film can be formed extremely well using the MOMBE method. Next, the SiO3 film is removed using a hydrofluoric acid-based etchant. Next, after masking the laser oscillation part with a resist or the like, a metal film 309 of gold or the like for an electrode is deposited. In the above example, 5iO7 was used as the mask material, but other dielectric films such as Si3N4, W, etc. can be used similarly. Also, Cd
Selective epitaxial growth of S, ZnTe, CdSe, etc. can also be performed, and the characteristics of the optical waveguide can be varied over a wide range. In this case, CdS, Zn, Te, Se
Each organic compound is used as a raw material.

Next, electrodes 105, 109, and 113 are installed by vapor deposition. A voltage is applied through wirings 106, 110, and 114, respectively. 106 is a laser driving power source; 110.
114 is a power source for adjusting the refractive index of each optical waveguide. Reflection surfaces 115 and 116 for forming an optical resonator are made completely flat by cleaving the crystal. Further, the reflective surface 115 is a (110) crystal plane. Also n Ga As
The surface of the substrate 101 is a (110) crystal plane. For example, gold is deposited on the surface of the end face 117 on one side of the laser resonator to reflect almost 100% of the laser beam, so that the laser light is not directly emitted from the end face 117. As a result, the wavelength-converted light 1
18 separations are possible. That is, it can be used independently as a wavelength-converted light source.

The selection of the wavelength to be converted is determined by the optical waveguide layers 107.1 on both sides.
12 by applying an electric field through electrodes 113, 110. That is, it is set based on the two electric field strengths and the difference between the two electric field strengths. Furthermore, the conversion efficiency of the light amount is 119.120.12
1, that is, the resonator length. In this embodiment, trial and error is carried out to determine the length of several millimeters. Furthermore, the laser oscillation wavelength can be changed by varying the value of X in Ax Ga+-x As;
It is also fully applicable to composition systems such as In As P system and AI Ga In P system. An example of the optical output is a semiconductor laser with a wavelength of 830 nm, a laser output of 50 mW, a wavelength variable range of 1130 to 530 nm, and an optical output of 1 to 1 mW.

In this embodiment, two optical waveguides, 119 and 120, are arranged, but it is also possible to use only one of them. However, the wavelength control accuracy and wavelength conversion efficiency are high in the case of two.

[Effect of the invention] As described above, the present invention has the following effects.

1. It is extremely compact and can be handled in the same way as a conventional IC chip.

2 Brainer integration is possible as a component of an optoelectronic integrated circuit.

3. Does not require a high-quality, large-sized non-linear optical crystal.

4. The thin film crystal for optical wavelength conversion can ensure high quality with high integrity through MOCVD ervicaxial growth, and high conversion efficiency can be obtained.

5. It is a useful wavelength tunable light source that can be coplanarly coupled to other types of optical waveguide devices using an optical waveguide.

6. The optical waveguide layer can be manufactured by the growth shown in Figure 1 and by the self-line process.

7. Since no etching process is required for the optical waveguide layer, an optical waveguide with low scattering loss can be produced without surface damage caused by etching.

8. Optical coupling between the laser resonator and the optical waveguide can be achieved with high efficiency.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view and a diagram schematically showing a planar structure of a light source according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing a typical conventional optical parametric excitation. FIGS. 3(a) to 3(d) are cross-sectional structural diagrams 8101...n showing the manufacturing process of an optical waveguide according to an embodiment of the present invention.
type GaAs substrate 102 - -...-n Al
x Ga+-x As(x=0.11103 ・-
---nGaAs104 ・105 ・106 ・107. 108, 112 ・ 109 ・ ・ ・ ・ 110 ・ ・ ・ ・ 113 ・ ・ ・ ・ 14 ・ l 5, l 7 ・ 18 ・ 19. 150 ・ 151 ・ ・P Alx Ga+-x As (x=0.1 thomic electrode/lead wire/Zn Sx Se+-++ epitaxial layer/Zn Se epitaxial optical waveguide layer/electrode film (Schottky barrier)/lead wire/ Electrode film (Schottky barrier) Lead wire/Reflecting surface (cleavage surface) Gold vapor deposited thin film/Wavelength converted light/Optical resonance lid part/N-type Ga As buffer layer/P Ga As 201. 202 ・ 204 ・ 205. 206・ 300 ・ 301 ・ 302 ・ 303 ・ 304. 306 ・ 307 ・ 308 ・ 309 ・ Reflector Laser crystal lens Reflector Nonlinear optical single crystal n-type Ga As Laser oscillation part Laser resonator Etching area 5i02 film etched Surface optical waveguide section Optical waveguide metal film Applicant: Seiko Epson Corporation

Claims (1)

[Claims] In a method for manufacturing a semiconductor light source in which a laser resonator and another optical waveguide are arranged on the same plane, I
1. A method for manufacturing a semiconductor light source, comprising a step of selectively epitaxially forming a group I-VI compound semiconductor.