JPS62208006A - Optical integrated circuit - Google Patents

Abstract

PURPOSE:To manufacture an element and a waveguide by continuous crystal growth by laminating element constituent layers on a substrate with a step part so that an active waveguide layer and a passive waveguide layer face each other on both sides of the step part. CONSTITUTION:The step part 11 parallel to the horizontal surface 16 of the substrate is formed at part of the substrate 10 by etching, and a buffer layer 17, the passive waveguide layer 18, an intermediate layer 19, the active waveguide layer 20, and a clad layer 21 are formed on the substrate 10 by continuous vapor-phase growth. In this case, the depth of the step 11 and the thicknesses of the layers 17 and 19 are so adjusted that the layers 20 and 18 face each other. A groove 22 is formed at the step boundary part to constitute a semiconductor laser 23 and a passive waveguide 24. Further, reflected light can be stopped from returning by forming a step part slanting to the surface 16. In this constitution, the element and waveguide are manufactured by the continuous crystal growth and the cost is reducible.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a semiconductor light-emitting device, a light-receiving device,
This field relates to the structure of optical integrated circuits in which waveguides and the like are formed by crystal growth.

[Background of the invention]

With the spread of optical fiber communication, optical functional elements such as semiconductor light emitting elements, light receiving elements, optical switches, and optical modulation elements, as well as passive elements such as optical branching elements, optical multiplexing/demultiplexing elements, and waveguides, are being mounted on semiconductor substrates. Research into so-called integrated optical integrated circuits has begun to be considered. An important challenge for this optical integrated circuit is to make it as simple as possible and mass-produce it using a through-process. As one solution to the above problem, the method shown in Figure 1 has been proposed (Japanese Unexamined Patent Publication No. 59-90981).
), an active waveguide 3 and a passive waveguide 5 are placed on the semiconductor substrate 1 on which a step extending in a direction perpendicular to the light propagation direction is formed, and an active waveguide 3 and a passive waveguide 5 are placed on both sides of the step, as shown in FIG. The waveguide and the passive waveguide are formed continuously through an intermediate layer so that their optical axes coincide, and then, as shown in (C),
Among the waveguides and the intermediate layer, portions above the step of the semiconductor substrate are removed to form groove surfaces substantially parallel to each other and facing each other in the active waveguide and passive waveguide. It has the characteristic that it can be realized by continuous crystal growth, and is expected to be economical. However, when we actually produced a prototype, we found the following problems. (
The semiconductor substrate in a) must be made by etching the surface 8 part, but since the surface 8 part is several times wider than the surface 9 part, one surface 8 is made flat and high. It turned out to be extremely difficult to manufacture with dimensional accuracy. It has been found that if the dimensional accuracy of this surface 8 portion deteriorates, it will adversely affect the performance of optical waveguides, optical modulators, optical switches, etc. formed on surface 8, making it impossible to obtain sufficient characteristics. In other words, since the number of optical devices formed on one surface 8 is several times greater than the number of optical devices formed on one surface 9, the dimensional accuracy on surface 8 is much higher than that on surface 9. High precision is required, and it has been found that it is difficult to improve the performance of optical devices with the substrate structure shown in FIG. 1(a). Furthermore, it has been found that because the end of the end face side 33 on the side to be etched cannot be formed neatly, when an optical fiber is connected to this end to transmit an optical signal, the optical coupling efficiency is significantly reduced. Ta.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical integrated circuit that can solve the above-mentioned conventional problems.

In other words, the structure of the optical integrated circuit is such that high-precision, high-performance semiconductor light-emitting devices, light-receiving devices, and passive waveguides can be manufactured by continuous crystal growth, and cost reduction can also be expected.

[Summary of the invention]

The present invention provides for a substrate such as a semiconductor, a ferroelectric material, a magnetic material, etc.
Semiconductor light emitting devices are used when constructing optical integrated circuits by forming semiconductor light emitting devices, light receiving devices, optical multiplexing/demultiplexing devices, optical modulation devices, optical switch devices, etc.

The part of the substrate where the light receiving element will be formed is etched to form a stepped part, and the buffer layer, passive waveguide layer, intermediate layer, active waveguide layer, and cladding layer are formed on the substrate to form the active waveguide layer and the passive waveguide. After continuous crystal growth is performed in order so that the layers face each other on both sides of the step, a groove is formed by etching in the vertical direction of the substrate in the vicinity of the first step, and a semiconductor light emitting device is formed using the previously scratched portion of the substrate. As a light receiving element, the remaining portion acts as a passive waveguide including an optical multiplexing/demultiplexing element, an optical modulation element, an optical switch element, etc.

[Embodiments of the invention]

2(a), (b), and (Q) show examples of substrates used in the optical integrated circuit of the present invention. Reference numeral 10 denotes a substrate, and for example, a semiconductor substrate (InP, GaAg, etc.) is used. 1
1, 12, and 13 are stepped portions provided on the substrate 1o,
It is formed by etching (eg, wet etching, dry etching). 16 is a horizontal surface of the substrate 10;
15 is a vertical surface perpendicular to the horizontal surface 16, and 14 is also a surface substantially perpendicular to 16. Reference numeral 11 denotes a stepped portion having a surface parallel to the horizontal surface 16. Reference numeral 12 denotes a stepped portion having a surface inclined at an angle θl with respect to the horizontal surface 16. This OL is an angle formed such that the 15 side is lower than the 14 side. 13 is a stepped portion having a surface inclined at an angle θ2 with respect to the horizontal plane 16, and 02 is an angle formed such that the 15 side is higher than the 14 side. A semiconductor light emitting device, or a semiconductor light emitting device and a light receiving device are formed on the surfaces of the step portions 11°12.13. On the other hand, on the horizontal plane 16, in addition to the passive waveguide, an optical modulation element, an optical switch element, an optical multiplexing/demultiplexing element, etc. are formed.
It has an area several times larger than the area of the part 2.13. In addition, the horizontal surface 16 is required to be flat and have a small surface roughness, but if the structure is as shown in FIG.
This has the advantage that very good characteristics can be obtained compared to the figure. That is, it is sufficient to use a highly accurate substrate for the horizontal surface 16 in advance, and since a vertical end surface is already obtained on the end portion 33 side, coupling with an optical fiber is also easy. θ1. θ2. The reason for having such an inclination angle is that in FIG. 1 (Q), the emitted light 7 from the active waveguide layer 3 of the semiconductor laser is reflected at the input part of the passive waveguide layer 5, and This is to prevent them from returning.

FIGS. 3(a) and 3(b) show an embodiment of the method and structure for manufacturing an optical integrated circuit according to the present invention. First, explanation will be given from FIG. The substrate (In
P) Form an InP buffer layer 17 on the layer 10. An InGaAsP passive waveguide layer 18 is formed thereon, and then,
InP intermediate layer 19, InGaAsP active waveguide layer 20 thereon, and finally InP cladding JjfJ21.
The six layers 17 to 21 forming the above can be formed by continuous vapor phase growth. Note that the InGaAsP active waveguide layer 2
The depth of the stepped portion 11, the buffer layer 17 and the intermediate layer 19 are such that the InGaAsP passive waveguide layer 18 and the InGaAsP passive waveguide layer 18 face each other.
The thickness of is set in advance. The step boundary shown in FIG. 3(a) is dry-etched to form a groove 22 as shown in FIG. 3(b), and the semiconductor laser 23 and passive waveguide 24 are
Note that the end face 15 side may also be etched to form a groove like 22 to form a resonant end face. By forming this groove portion 22, a resonant end face of the semiconductor laser 23 is obtained, and an optical signal lased between it and the other end face 15 is emitted as shown by an arrow 25 and propagated within the passive waveguide 18.

The passive waveguide section 24 is not shown in this figure.

In reality, it includes an optical multiplexing/demultiplexing element, an optical modulation element, an optical switching element, etc., and has an area several times larger than the area of the semiconductor laser section 23.

FIGS. 4(a) and 4(b) show another embodiment of the optical integrated circuit of the present invention. In the figure (a), both side end faces 27 and 28 of the groove portion 26 are inclined by an angle of θ8°0 to prevent the reflected light from the variable waveguide layer 18 from returning to the active waveguide layer 19 of the semiconductor laser portion 23. This is what I did. Effective in reducing reflected noise. It also has the effect of changing the resonance conditions of the semiconductor laser 23, and is effective, for example, in making a distributed feedback type or distributed reflection type laser into a dynamic uniform mode. In the figure (b), the active waveguide layer 19 is opposed to the passive waveguide layer 18 so that it is located approximately in the middle, and the emitted light 29 from the active waveguide layer 19 is efficiently coupled into the passive waveguide layer 18. This is how it was done.

FIGS. 5(a) and 5(b) show an embodiment of the method for manufacturing an optical integrated circuit according to the present invention and its structure. In this case, the area of part 11 in Fig. 2(a) is set slightly larger and each layer is grown in a continuous vapor phase, as shown in Fig. 2(b).
As shown in the figure, two grooves 22 and 31 are formed. The reference numeral 23 serves as a semiconductor laser section, and the reference numeral 30 serves as a light receiving element section for monitoring the emitted light 32 of the semiconductor laser.

As described above, according to this embodiment, the semiconductor laser section, the light receiving element section, and the passive waveguide section 24 can be continuously formed by vapor phase growth. Therefore, costs can be reduced, and the top surface 16 of the substrate that forms the passive waveguide section is flat and surface roughness can be reduced, making it possible to form high-performance optical devices with various functions in this area. It becomes possible.

The present invention is not limited to the above embodiments. for example.

The semiconductor laser section may be a distributed feedback type or distributed reflection type laser.

〔Effect of the invention〕

According to the present invention, highly accurate and high-performance semiconductor light emitting devices, light receiving devices, and passive waveguides can be manufactured by continuous crystal growth. As a result, mass production is possible and cost reduction can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional method for manufacturing an optical integrated circuit. FIG. 2 is a diagram showing an embodiment of the substrate used in the optical integrated circuit of the present invention, FIGS. 3 and 5 are diagrams showing an embodiment of the method of manufacturing the optical integrated circuit and its structure, and FIG. 1 is a diagram showing an embodiment of an optical integrated circuit according to the present invention. 1.10...Substrate, 2,17...Buffer layer, 3゜20...Active waveguide layer, 4,19...Intermediate layer, 5゜18...Passive waveguide layer, 6, 21... cladding layer,
7゜25.29', 32...Arrow indicating the direction of light propagation, 8゜11, 12, 13...Stepped portion, 9,16...
Horizontal surface part, 14.15... Vertical surface, 23... Semiconductor laser part, 24... Passive waveguide part, 22, 26, 31
...Groove, 27.28...Side end surface e
,, ,-t, Agent Patent Attorney Katsuma Ogawa"・20.゛'-(- Figure 3 (a-ji (b) η Y 4 Figure (a-) (b) Mayo 5 Figure (L) (b )

Claims (1)

[Claims] 1. The upper surface of the substrate where the semiconductor optical device is to be formed is cut to provide a stepped portion, and a buffer layer, a passive waveguide layer, an intermediate layer, an active waveguide layer, and a cladding layer are formed on this substrate. , an optical integrated circuit characterized in that the active waveguide layer and the passive waveguide layer face each other on both sides of a stepped portion. 2. In claim 1, a groove portion is formed in the vicinity of the step portion by vertical etching from the upper layer toward the substrate, and the active waveguide layer and the passive waveguide layer are substantially parallel to each other. An optical integrated circuit characterized by forming an end face facing the. 3. The optical integrated circuit according to claim 1, characterized in that the top surface of the chipped substrate has a slope. 4. The optical integrated circuit according to claim 2, wherein at least one groove is formed in the layer formed in the cut portion of the substrate in a direction perpendicular to the layer.