JPH09265020A - Optical integrated element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical integrated element which has a planar characteristic, has the high allowance to dimensional accuracy and is integrated with optical passive elements which are easily manufactured by integrating the optical passive elements formed by oxidizing part of semiconductor layers consisting of aluminum as their constituting element, thereby constituting the integrated element. SOLUTION: An optical waveguide is constituted by integrating the optical passive elements obtd. by oxidizing part of InAlAs 12 which is the semiconductor layers consisting of the aluminum as their constituting elements. This process for production comprises epitaxially growing an InAlas layer and an InP clad layer 11 on InP substrate 14. Waveguides are thereafter patterned on this InP clad layer 11.' The InP clad layer 11 and the selectively oxidized InAlAs layers 13 are removed down to the InP substrate 14 exclusive the prescribed regions by selective etching. Only the selectively oxidized InAlAs layers 13 are oxidized down to mid-way exclusive InAlAs cores 12, by which the selectively oxidized InAlAs layers 13 are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical integrated device in which optical passive devices are integrated.

[0002]

2. Description of the Related Art A semiconductor two-dimensional integrated optical device including a surface emitting laser is expected as a device for optical information processing and optical interconnection for optical communication. In a semiconductor two-dimensional integrated optical device, it is important to simplify the device manufacturing process because the device can be provided at low cost.

Conventionally, as a method of manufacturing a passive element such as a polarizer, a Fresnel lens, and an optical waveguide on a semiconductor two-dimensional integrated optical element, a thin wire pattern of oxide such as silicon dioxide is used as a diffraction grating on the semiconductor. Have been used.

There are the following two types of methods for producing the fine wire pattern. First thin line pattern manufacturing method: First, a method of patterning with a resist, then applying an oxide to the entire surface by a method such as sputtering, and then removing an excess oxide by a lift-off process or the like. Second fine line pattern manufacturing method: First, after applying oxide on the entire surface, patterning with a resist or the like, and then using chemical etching using hydrofluoric acid or the like, or reactive ion etching using CF ₄ or the like. This is a method of removing excess oxide.

[0005]

However, the above method has the following problems. In the first method, it is necessary to accurately control the shape of the resist cross section. In the second method, there is a risk of using hydrofluoric acid or the like and a time-consuming dry etching step is required.

Further, since the difference in the refractive index between the substance forming the element and the air is large, the size of each component of the element is small and the manufacturing tolerance thereof is small, which makes the manufacturing difficult. Furthermore, since the planar structure cannot be used, the manufactured element has a drawback that it is greatly affected by the sectional accuracy.

In view of the above prior art, it is an object of the present invention to provide an optical integrated device in which optical passive devices having planarity, large tolerance for dimensional accuracy and easy to manufacture are integrated.

[0008]

An optical integrated device according to the present invention for solving the above problems is an integrated optical passive device obtained by oxidizing a part of a semiconductor layer containing aluminum (Al) as a constituent element. It is characterized by.

At room temperature, a semiconductor containing aluminum (Al) is relatively easily oxidized under high temperature steam as compared with a semiconductor not containing aluminum (Al), and the oxide has a smaller refractive index than the semiconductor and is very stable. Is.
In addition, the oxide has almost the same volume as the semiconductor before oxidation, and has a refractive index in the middle of that of the semiconductor and air. Therefore, the surface aluminum (A
By partially oxidizing the semiconductor layer containing l), it is possible to easily introduce a refractive index difference into the plane without impairing the planarity, and to integrate stable optical passive elements with a large manufacturing tolerance. It is possible to fabricate the integrated optical device.

[0010]

Embodiments of the present invention will be described below.

(First Embodiment) FIG. 1 shows an optical waveguide on an InP substrate according to an embodiment of the present invention. In FIG. 1, reference numeral 11 is an InP clad layer, 12 is an InAlAs core, 1
3 shows an InAlAs selective oxidation layer, and 14 shows an InP substrate. As shown in FIG. 1, an optical waveguide, which is a type of optical integration, has a structure in which InAlAs (12), which is a semiconductor layer containing aluminum (Al) as a constituent element, is partially oxidized.
An optical passive element formed by forming an AlAs selective oxidation layer (13) is integrated.

The method of manufacturing the optical waveguide on the InP substrate will be described below. First, an InAlAs layer and then an InP clad layer are epitaxially grown on the InP substrate (14). Then, the waveguide pattern is patterned on the InP clad layer by electron beam drawing using a resist,
Cladding layer (11) and InAlAs selective oxidation layer (13)
And are removed to the InP substrate (14) by selective etching, leaving the striped regions. Then, only the InAlAs selective oxidation layer patterned in a striped pattern in a high temperature steam atmosphere is partially oxidized while leaving the InAlAs core (12) which is the core part, and the InAlAs selective oxidation layer (13) is formed to form the waveguide structure. Form.

It was confirmed that light of 1.3 μm was incident on the optical waveguide on the InP substrate thus manufactured by a semiconductor laser and the light was guided.

(Second Embodiment) FIG. 2 is a sectional view of a 0.85 μm polarization control surface emitting laser manufactured according to the present invention. In FIG. 2, reference numeral 21 is AlGaA that is not oxidized.
s, 22 is AlGaAs oxide, 23 is p electrode, 24 is p-AlAs / AlGaAs DBR, 25 is p-Al
GaAs clad layer, 26 is AlGaAs active layer, 27
Is n-AlGaAs cladding layer, 28 is n-AlAs /
AlGaAs DBR, 29 is an n-GaAs substrate and 3
0 indicates each n-electrode.

A method of manufacturing a 0.85 μm polarization control surface emitting laser will be described below. First, n-AlAs and n are deposited on the n-GaAs substrate 29.
25 pairs of AlGaAs and AlGaAs are alternately grown at a film thickness of 1/4 of the optical wavelength to form n-AlAs.
/ AlGaAs DBR (28) reflector is formed. Then, the n-AlGaAs clad layer (27), A
The 1GaAs active layer (26) and the p-AlGaAs cladding layer (25) are epitaxially grown. Then, the waveguide pattern is patterned on the InP clad layer by electron beam drawing using a resist,
The clad layer and the InAlAs selective oxide layer are removed by selective etching while leaving striped regions. Subsequently, 20 pairs of p-AlAs and p-AlGaAs are alternately epitaxially grown at a film thickness of ¼ of the optical wavelength to form p-AlAs / AlGaAsDBR.
(24) Form a reflecting mirror. After that, AlGaAs subjected to selective oxidation having a larger Al composition than p-AlGaAs forming the p-side reflecting mirror
Layer, GaAs cap layer is epitaxially grown.

After performing the above-mentioned steps, 30
A resist pattern of μm × 30 μm is formed, and the above epitaxial growth layer is etched to the n-GaAs substrate (29). After that, apply 20
After forming a pattern of μm × 20 μm and selectively etching the GaAs cap layer, a G of 20 μm × 20 μm is formed.
Form the aAs1 cap region. Next, this GaA
After forming a grid-shaped resist pattern in the s region by an electron beam drawing method, the GaAs cap layer is selectively etched to form a grid-shaped GaAs layer.

After that, in a high temperature steam atmosphere, only a portion of the layer laminated under the GaAs layer which is not covered with the GaAs cap layer is oxidized to form an AlGaAs oxide (22) layer, and a polarizer is formed. Form. afterwards,
The lattice-shaped GaAs cap layer is removed.

Then, AuGeN is continuously formed on the entire lower surface.
After depositing i / Au to form an n-electrode (30) and forming a pattern with a resist on the upper surface side, AuGeNi / A
u is vapor-deposited and lift-off is performed to form a p-electrode (23). Finally, alloying is performed in a hydrogen atmosphere at 425 ° C. to make the electrode ohmic.

The polarization characteristics of the polarization control surface emitting laser configured as described above were measured.
An extinction ratio of 30 dB with polarized light was confirmed.

(Third Embodiment) FIG. 3 is a sectional view of a semiconductor selective oxidation type Fresnel lens made by the present invention. In FIG. 3, reference numeral 31 is an InAlAs oxide, 32 is an unoxidized InAlAs, and 33 is an InP substrate. A Fresnel lens array can be constructed by arranging the Fresnel lenses one-dimensionally or two-dimensionally in the same plane.

A method of manufacturing the semiconductor selective oxidation type Fresnel lens will be described below. First, an InAlAs layer and then an InP cap layer are epitaxially grown on the InP substrate (33). Then, the Fresnel lens pattern is patterned on the InP layer using a resist using an electron beam drawing apparatus, and only the InP cap layer is removed by selective etching. Then, in the InAlAs layer in a high-temperature steam atmosphere, only the part not covered with the InP cap layer is oxidized to form an InAlAs oxide (31) layer and an unoxidized InAlAs (32) layer. Finally, the remaining InP cap layer is all removed to form a semiconductor selective oxidation type Fresnel lens.

A laser beam of 1.3 μm obtained by collimating a semiconductor laser with a beam expander was incident on the semiconductor selective oxidation type Fresnel lens manufactured as described above, and the focal length was measured with a beam profiler. The focal point was about 12 mm. I confirmed that it is a lens.

[0023]

As described above in detail with reference to the embodiments, according to the two-dimensional integrated device including the process of the present invention, the selective oxidation of the semiconductor containing aluminum (Al) while maintaining the planarity is achieved. A passive optical device having a large manufacturing tolerance can be easily manufactured by combining a low refractive index layer introduced by using and an unoxidized semiconductor which is a material having a relatively high refractive index.

As a result, an integrated optical device for optical information processing, optical communication, optical interconnection, and optical subscriber system, in which optical passive devices are integrated, can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical waveguide on an InP substrate according to an embodiment of the present invention.

FIG. 2 is a sectional view of a 0.85 μm polarization control surface emitting laser according to an embodiment of the present invention.

FIG. 3 is a sectional view of a semiconductor selective oxidation type Fresnel lens according to an embodiment of the present invention.

[Explanation of symbols]

 11 InP 12 InAlAs core 13 InAlAs selective oxidation layer 14 InP substrate 21 unoxidized AlGaAs 22 AlGaAs oxide 23 p electrode 24 p-AlAs / AlGaAs DBR 25 p-AlGaAs cladding layer 26 AlGaAs active layer 27 n-AlGaAs cladding layer 28 n-AlAs / AlGaAs DBR 29 n-GaAs substrate 30 n-electrode 31 InAlAs oxide 32 unoxidized InAlAs 33 InP substrate

Claims (1)

[Claims] 1. An optical integrated device comprising an optical passive device integrated by oxidizing a part of a semiconductor layer containing aluminum (Al) as a constituent element.