JPH04129270A - Manufacture of optical integrated circuit device - Google Patents

Abstract

PURPOSE:To make a flat part of the title device operate as an active layer of a semiconductor laser and its uneven part operate as an optical guide element due to effective extension of an energy band gap by quantum size effect by forming the uneven part for exposing a surface having a special surface index on the flat surface of an InP substrate. CONSTITUTION:An uneven part for exposing a surface having a face index (111) is selectively formed on a flat surface of an InP substrate (e.g. an n-type InP substrate 21) having a face index (100). Then, a barrier film (e.g. an InGaAsP barrier film 22A) and a compound semiconductor thin film to become a well film (e.g. an InGaAs well layer 22B) are grown on the entire surface to form a multiple quantum well (e.g. a multiple quantum well 22) thick in the degree of operating as an active layer of a semiconductor laser (e.g. a light emitting element part 40) on a flat part and thin in the degree of operating as an optical guide element (e.g. an optical guide element part 50) due to effective extension of an energy band gap by a quantum size effect on an uneven part.

Description

[Detailed Description of the Invention] [Summary] Regarding a method suitable for manufacturing an optical integrated circuit device in which a light emitting element and an optical waveguide element are integrated on the same substrate, light emitting elements having different energy band gaps. The purpose is to make it possible to form the active layer of the active layer and the guide layer of the optical waveguide element on the same substrate in one growth, and to realize smooth connection between them. ) is formed on the flat surface of an InP substrate with unevenness that exposes a plane with a plane index of (111),
Next, a multi-quantum well is formed, which is thick enough to act as an active layer of a semiconductor laser in the flat part and thin enough to act as an optical waveguide element in the uneven part, where the energy band gap effectively widens due to the quantum size effect. form,
After that, the method is configured to include a step of forming an electrode for passing a current through a region of the multiple quantum well located on a flat portion to act as an active layer of a semiconductor laser.

(Industrial Application Field) The present invention relates to a method suitable for manufacturing an optical integrated circuit device in which a light emitting element and an optical waveguide element are integrated on the same substrate.

Currently, with the demand for higher capacity and faster optical communication systems, research and development is actively being conducted to integrate light emitting elements and optical waveguide elements on the same substrate. There are many difficulties in smoothly connecting the waveguide layer of the optical waveguide element, and it is necessary to solve these problems.

[Conventional technology]

6 to 9 are cutaway side views of essential parts of an optical integrated circuit device at key points in the process for explaining a conventional method for manufacturing an optical integrated circuit device. I will explain while referring to it.

See Figure 6 metalorganic vapor phase epitaxy.
por phase epitaxy:MOVPE
) method, an InGaAsP guide layer 2.) is formed on the InP substrate 1. 1nGaAsP active layer 3. Grow a 1nP cladding 114.

See Figure 7 chemical vapor deposition (chemical vapor deposition)

A 5ift film 5 is formed by applying a CVD method.

The 5iOzliE5 is patterned by applying a conventional photolithography technique to leave a portion covering the light emitting element region and remove the other portion.

Using the SiO□ film 5 as a mask, selective etching is performed from the surface of the 1nP cladding 14 to the surface of the InP substrate 1 to create a space where an optical waveguide element is to be formed.

Referring to FIG. 8, by applying the MOVPE method, an InGaAsP guide layer 6 is formed on the InP substrate 1. A 1nP cladding layer 7 is grown.

In this case, as a selection criterion for the material constituting the guide layer 6, it is considered that the guide layer 6 is a semiconductor material having a light absorption edge on the shorter wavelength side compared to the emission wavelength of the light emitting element.

Referring to FIG. 9, the Sin film 5 used as an etching mask is removed.

By applying the MOVPE method, an InPn layer 5 and an InGaAsP contact layer 9 are grown in this order.

After this, electrodes etc. are formed to complete the process.

In this conventional example, the case where the optical waveguide element is embedded is explained, but conversely, the light emitting element is also embedded and formed, and in that case, the step 6-(1) is performed. Instead, 6-(1)' InGaAs P guide layer 6 and InP cladding N7
grow.

Similarly, instead of step 7-(2), 7-(2)' The St○2 film 5 is patterned to leave a portion covering the optical waveguide element region.

Similarly, instead of step 7-(3), using the SiO□ film 5 as a mask, selective etching is performed from the surface of the InP cladding layer 7 to the surface of the InP substrate 1 to create a space where a light emitting element is to be formed. Generate.

Similarly, instead of step 8-(1), 8-(1)' On the exposed InP substrate 1, InGaAs P guide layer 2, InGaAsP active layer 3, InP cladding layer 4, grow.

In this case, as a selection criterion for the material constituting the active layer 3,
It is considered that the semiconductor material has an emission wavelength on the long wavelength side compared to the optical absorption edge wavelength of the optical waveguide element.

The process is as follows.

[Problems to be Solved by the Invention] As explained above, in the conventional technology, the portion related to the light emitting device and the portion related to the optical waveguide device are grown separately.

This is because the energy band gap of the active layer 3 in the light emitting device is different from that of the guide layer 6 in the optical waveguide device. That is,
In the guide N6 in the optical waveguide element, energy and
It is necessary to widen the band gap so that the light emitted from the active layer 3 can propagate without being absorbed.

By the way, as mentioned above, when the parts related to the light emitting element and the part related to the optical waveguide element are grown in two steps, not only the number of manufacturing steps increases, but also the growth of the parts related to the light emitting element and the optical waveguide element. There is a problem that the connection is not established properly.

FIG. 10 shows a cutaway side view of a main part of an optical integrated circuit device for explaining the problem of the connection relationship between a light emitting element and an optical waveguide element.
The same symbols as those used in FIGS. 6 to 9 represent the same parts or have the same meaning.

In the figure, reference numeral 10 indicates a gap created when the connection between the light emitting element and the optical waveguide element fails to grow.

In the illustrated state, the light from the light emitting element is absorbed or reflected by the gap 10 and cannot be sufficiently guided to the optical waveguide element.

The present invention makes it possible to form the active layer of a light-emitting device and the guide layer of an optical waveguide device, which have different energy band gaps, on the same substrate by one-time growth, and to smoothly connect them. try to make it come true.

[Means to solve the problem]

1 and 2 are cross-sectional side views of essential parts of an optical integrated circuit device for explaining the present invention in detail, and the following explanation will be made with reference to these figures.

First, FIG. 1 will be explained.

Corrugations are formed on the surface of the InP substrate 11 having a plane index of (100) so that a plane having a plane index of (111)A or (111)B is exposed.

A compound semiconductor crystal film 12 such as InP, InGaAsP, or InGaAs is grown.

As described above, the present inventor has developed an InP substrate 1 having unevenness.
When compound semiconductor crystal film 12 is grown on InP
Compound semiconductor crystal l in the uneven portion of the substrate 11
It has been experimentally found that the growth rate of l112 is slower than that in flat areas.

Therefore, the compound semiconductor crystal film 12 is thick in the flat portion, and
In addition, it becomes thinner at uneven parts, S,>S.

It is.

Next, FIG. 2 will be explained. It should be noted that, based on this explanation, it will be understood that by utilizing the phenomenon explained with reference to FIG. 1, a multiple quantum well with a very useful configuration can be obtained.

An InGaAsP barrier film 13A and an InGaAs
A multi-quantum well 13 is formed by laminating a required number of well membrane layers.

In this way, the barrier layer 13A and the well [513B] are formed thickly in the flat portions of the InP substrate 11, and thinly formed in the uneven portions, just as described above. Therefore, in areas with unevenness, the spread of the energy band gap of the quantum well structure due to the quantum size effect becomes larger than in areas without unevenness. In addition, in Figure 2,
Further, on the multiple quantum well 13, I nCyaAs P
A light blocking layer 14 and an InP cladding layer 15 are laminated.

As described above, in the compound semiconductor film formed on the InP substrate 11, the energy band gap is narrow in the thick portion and widened in the thin portion.

For these reasons, in the method for manufacturing an optical integrated circuit device according to the present invention, (1) an InP substrate with a plane index of (100) (for example, n
On the flat surface of a type InP substrate 21), unevenness that exposes a plane with a plane index (111) is selectively formed, and then on the flat part of the InP substrate, unevenness that grows quickly and consists of a (111) plane is formed. Taking advantage of the fact that growth is slow in some parts, a barrier film (for example, InGaAsP barrier film 22A) and a compound semiconductor thin film (for example, InGaAsP barrier film 22A) and a well film (for example, InGaAs well film) and a compound semiconductor thin film that will become a 2-well film are grown on the entire surface, and in flat parts, a semiconductor laser (
For example, in a part that is thick enough to act as an active layer of the light emitting element part 40) and has an uneven surface, energy is absorbed due to the quantum size effect.
A multiple quantum well (e.g., multiple quantum well 22) is formed thin enough to effectively widen the band gap to act as a leading wave element (e.g., optical waveguide portion 50), and then forming electrodes (for example, the p-side electrode 22 and the n-side electrode 30) for passing a current that acts as an active layer of the semiconductor laser through a thick portion with a narrow energy band gap on the portion;
(2) In (1) above, the part of the multiple quantum well that is thin and has a wide energy band gap on the uneven part is changed in wavelength of laser light or (3) In (1) above, the surface index (111) is (
111) A, or (4) In (1) above, the surface index (111) is (
111) It is characterized by being B.

[Effect]

By adopting the above method, the quantum size effect in a thin semiconductor film formed on an uneven part is larger than that in a thick semiconductor film formed on a flat part, and therefore the energy band・The gap becomes effectively wider, and the light generated in the semiconductor film on the flat part, that is, the active layer of the light emitting element, is transmitted to the semiconductor film on the uneven part, that is, in the active layer of the light emitting device.
It can propagate well through the guide layer of the optical waveguide element, and since these semiconductor films are grown at the same time, the connecting parts are completely integrated and there are no gaps. .

〔Example〕

FIGS. 3 to 5 are side views (FIGS. 3 and 4) cut away from the main parts of an optical integrated circuit device at key points in the process for explaining one embodiment of the present invention, and a front view cut away the main parts (FIGS. 3 and 4). 5), and will be explained below with reference to these figures. FIG. 4 is an enlarged representation of the broken line circle shown in FIG. In addition, in this embodiment, a distributed reflector (distributed-b
The present invention deals with the case where a light emitting element consisting of a rag reflector (DBR) type semiconductor laser is combined with an optical waveguide element and formed on the same substrate.

Refer to Figure 3. By applying resist process in photolithography technology, interference exposure method, and chemical wet etching method, n-type InP with a surface index of (100) is produced.
On the surface of the substrate 21, concavities and convexities are formed, which are diffraction gratings for a DBR type laser. In the case of this embodiment, the other reflector is an open-arm surface as in a normal Fabry-Perot type semiconductor laser.

In this etching, by using a hydrochloric acid-based etching solution as an etchant, the surface index of the uneven surface can be set to (111)A. Here, the wavelength of the laser light generated by the light emitting element portion 40 is approximately 1
．． In order to selectively reflect light of 5 μm to the light emitting element portion 40, the pitch of the diffraction grating made up of the unevenness is approximately 24 μm.
0 (nm), and the depth of the unevenness is approximately 150 (nm).
And so.

Lightly etch the entire surface using a sulfuric acid-based etching solution.

3-(3) (See also Figure 4) Metalorganic vapor deposition
por phase epitaxy:MOVPE
) method, the emission wavelength is 1.1 [μm].
InGaAsP barrier film 22 with a composition of ~1.3 [μm]
A multiple quantum well 22 is formed by alternately stacking A and InGaAs well films 22B.

In this case, the thickness of each of the barrier film 22A and the well film 22B was approximately 7 (nm) in the flat portion, that is, the light emitting element portion 40, and the number of periods was 5 to 10. In addition, for the sake of experiment, a large number of samples with various periods were prepared.

As a raw material gas, trimethylindium (TM I n s ((, H
3) 3In), triethyl gallium (TEGa: (Cz Hs
)3Ga), phosphine (PHI:) for P, arsine (
AsH, ) was used, and hydrogen gas was used as the carrier gas. The total flow rate of gas supplied to the growth chamber is 3 to 10 (
f/min], the growth temperature was about 600 ('C), and the growth pressure was about 0.1 [atmospheric pressure]. The growth rate has a plateau, i.e.
0 in the part that is not a diffraction grating. 5 Cμm:l ~2.
Of: μm).

By continuing to apply the MOVPE method, p-type I
An nGaAsP optical confinement layer 23 is formed.

The main data of this optical confinement layer 23 are as follows.

Composition: Approximately 1.1 [μm] in emission wavelength Thickness: Approximately 0.3 [μm] Impurity concentration: l x l O” [cm-J same <M
A p-type InP cladding layer 24 is formed by applying the OVPE method.

The main data regarding this cladding layer 24 are as follows.

Thickness: Approximately 0.4 [μm] Impurity concentration: 2 x 10” (C1m-”) 5th
See figure chemical vapor deposition.

ur deposition:CVD) method, photo・
By applying a resist process in lithography technology, a chemical wet etching method, etc., using a striped SiO
Mesa etching is performed on a part of the multiple quantum well 22 and the n-type 1nP substrate 21 to form a stripe mesa.

By applying the MOVPE method, the stripe S
In, using the film as a mask, a p-type 1nP block layer 25 and an n-type 1nP block layer 26 are formed to bury the mesa.

The main data of each semiconductor layer grown here are as follows.

(a) Thickness of block layer 25: 1 [μm] Impurity raw material Nidimethylzinc (DMZn: (CH3)zZn) Impurity concentration:
I X I O"(cm-": 1 (b) block 12
Thickness for 6: 0.3 [μm] Impurity raw material: Monosilane (SiH4) Impurity concentration: 2 × 10” (cll-”) After removing the Sin film used as a mask, MOVPE
By applying the method, the p-type 1nP cladding layer 27,
A p-type 1 nGaAsP:] contact layer 28 is formed.

The main data of each semiconductor layer grown here are as follows.

(a) Thickness of cladding layer 27: 2 [μm] Impurity: DMZn Impurity concentration = 5 × 1017 [c'l11-3] (9) Thickness of contact layer 28: O, aCμm] Impurity: DMZn Impurity concentration: The p-side electrode 29 and the n-side electrode 30 are formed by applying a vacuum evaporation method.

Examples of main data regarding the electrodes 29 and 30 are as follows.

(a) Material for the electrode 29: Ti/Pt-Au (b) Material for the electrode 30: Au/5n-Au In the above embodiment, the DBR type laser, which is a light emitting element, and the optical waveguide element were formed on the same substrate. Although the optical integrated circuit device is described, the invention is not limited thereto. For example, an independent electrode may be formed not only in the light emitting element portion 40 but also in the leading wave element portion 50, and a forward bias voltage may be applied to the optical waveguide element portion 50. A light emitting element that can operate as a wavelength tunable laser or a laser with an optical modulator by applying a reverse bias voltage to change the refractive index or by applying a reverse bias voltage to change the optical absorption coefficient,
It is also possible to realize an optical integrated circuit device by forming this and an optical waveguide element as described above at the same time.

〔Effect of the invention〕

In the method for manufacturing an optical integrated circuit device according to the present invention, irregularities are formed to expose a plane with a plane index of (111) on a flat surface of an InP substrate with a plane index of (100). Forming a multi-quantum well that is thick enough to act as an active layer of a semiconductor laser in some parts and thin enough to effectively widen the energy band gap in uneven parts due to the quantum size effect and act as an optical waveguide element; An electrode for passing a current to act as an active layer of a semiconductor laser is formed in a region located on a flat portion of the multiple quantum well.

By adopting the above method, the quantum size effect in a thin semiconductor film formed on an uneven part is larger than that in a thick semiconductor film formed on a flat part, and therefore the energy band・The gap becomes effectively wider, and the light generated in the semiconductor film on the flat part, that is, the active layer of the light emitting element, is transmitted to the semiconductor film on the uneven part, that is, in the active layer of the light emitting device.
It can propagate well through the guide layer of the optical waveguide element without being absorbed, and since these semiconductor films are grown at the same time, the connecting parts are completely integrated. There are no gaps at all. Further, by selecting the pitch of the uneven portion to correspond to the wavelength of the propagating light, the uneven portion can sufficiently serve as a reflector that selectively reflects only that light to the light emitting element portion.

[Brief explanation of drawings]

1 and 2 are cut-away side views of essential parts of an optical integrated circuit device for explaining the present invention in detail, and FIGS. 3 to 5 are main process steps for explaining an embodiment of the present invention. The main part cutaway side view (Fig. 3, Fig. 4), main part cutaway front view (Fig. 5), and Figs. 6 to 9 of the optical integrated circuit device show the method of manufacturing the optical integrated circuit device. FIG. 10 is a cutaway side view of the main parts of an optical integrated circuit device at important process points to explain a conventional example, and FIG. Each shows a cutaway side view of the main part. In the figure, 21 is an n-type 1nP substrate, 22 is a multiple quantum well, 22A is an InGaAsP barrier film in the multiple quantum well 22, 22B is an InGaAs well film in the multiple quantum well 22, and 23 is a P-type InGaAsP optical confinement layer, 24 is P type 1
nP cladding layer, 25 is p-type 1nP block layer, 26 is n-type 1nP block layer, 27 is P-type InP cladding layer, 28 is p-type 1nGaAs P contact layer, 29 is P
30 is an n-side electrode, 40 is a light emitting element portion, and 50 is an optical waveguide element portion. Patent Applicant Fujitsu Ltd. Representative Patent Attorney Akira Aitani Representative Patent Attorney Hiroshi Watanabe - Figure 1 Figure 2 40: Light emitting element portion 50: Leading wave element portion Figure 3 #J4 Figure C) Figure 7 Figure 8 Copper Figure 9 Glazed Figure 10

Claims (4)

[Claims] (1) Selectively form irregularities that expose a plane with a plane index of (111) on the flat surface of an InP substrate with a plane index of (100), and then grow on the flat part of the InP substrate. Fast and (
111) Taking advantage of the fact that growth is slow in uneven areas consisting of planes, a compound semiconductor thin film to be used as a barrier film and well film is grown over the entire surface, and the uneven areas are thick enough to act as an active layer of a semiconductor laser on flat areas. In this method, a multi-quantum well is formed which is thin enough to effectively widen the energy band gap due to the quantum size effect and can act as an optical waveguide element, and then a thick and thin multi-quantum well is formed on the flat part of the multi-quantum well. 1. A method of manufacturing an optical integrated circuit device, comprising the step of forming an electrode for passing a current through a portion having a narrow energy band gap to act as an active layer of a semiconductor laser. (2) An independent electrode for flowing current that allows the thin part with a wide energy band gap on the uneven part of the multi-quantum well to act as an optical waveguide element that changes the wavelength of laser light or modulates the light. 2. The method of manufacturing an optical integrated circuit device according to claim 1, further comprising the step of forming. (3) The method for manufacturing an optical integrated circuit device according to claim 1, wherein the plane index (111) is (111)A. (4) The method for manufacturing an optical integrated circuit device according to claim 1, wherein the plane index (111) is (111)B.