JPH0389579A - Semiconductor optical integrated element and manufacture thereof - Google Patents

Abstract

PURPOSE:To facilitate manufacture and achieve optical coupling efficiency of about 100% by causing a light emitting region to include an active layer consisting of multiple quantum well structure and causing a light modulating region to include a semiconductor layer in which multiple quantum well structure is randomized. CONSTITUTION:A distributed feedback type semiconductor (DFB) laser region 100 includes an active layer consisting of a semiconductor layer (MQW layer) 30 with multiple quantum well structure, and a modulator region 200 includes a semiconductor layer (MQW randomized layer) 40 in which multiple quantum well structure, same as that of the active layer, is randomized. DFB laser light can be modulated by applying an electric field to the MQW randomized layer 40 due to Franz-Keldysh effect. Because the MQW randomized layer 40 is optically continuously connected to the original MQW layer 30, optical scattering is scarcely found at the boundary part between the DFB laser region 100 and the light modulator region 200 so that coupling efficiency of nearly 100% can be achieved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the structure and manufacturing method of a semiconductor optical integrated device, and particularly relates to the structure and manufacturing method of a semiconductor optical integrated device that utilizes a multiple quantum well structure and its disordering. .

[Conventional technology]

Semiconductor optical integrated devices, in which a light-emitting region and a modulation region that modulates the light emitted from the light-emitting region are integrated on a single semiconductor substrate, are important as small, high-performance light sources for high-speed optical fiber communications. be. Among these, semiconductor optical integrated devices that integrate distributed feedback semiconductor lasers (hereinafter referred to as DFB lasers) and absorption optical modulators play a central role as light sources for optical fiber communications of several Gb/s or more. It is expected that this will be fulfilled. There are roughly three types of conventional DFB laser and optical modulator integrated elements:
Each optical modulator has its own characteristics. The first is one that utilizes the Franz Keldeitssch effect in an optical modulator.
The transmitted laser light is modulated by applying an electric field. Regarding this semiconductor optical integrated device, there is a report by Suzuki et al., for example. (M,5uzuki et al., IEEE
J, Lightwave Tech.

LT-5, (1987) 1277), the second is one that utilizes the quantum confined Stackle effect in an optical modulator,
The transmitted DFB laser light is modulated by applying an electric field to the multiple quantum well layer formed in the optical modulator region.

Regarding this semiconductor optical integrated device, there is a report by Yozai et al. (Y, Kawamura et at, IEEE
J, Quantua+Electron, QE-2
3, (1987) 915). In the first and second conventional examples described above, the DFB laser region and the optical modulator region are composed of semiconductor layers having different compositions. For this reason, in manufacturing, a method is used in which a DFB laser region is first grown as a crystal on a semiconductor substrate, and then an optical modulator region is selectively grown as a crystal.

The third conventional example utilizes gain modulation in an optical modulator, and the optical modulator region has an active layer having the same composition as the DFB laser region, and the injection into the active layer of the optical modulator region is By modulating the current, the gain is changed and the transmitted DFB laser light is modulated. Regarding this semiconductor optical integrated device, there is a report by Yamaguchi et al.
at, Electron, Lett.

23, (1987) 190>. In the third conventional example, D
Since the FB laser region and the optical modulator region are composed of semiconductor layers having the same composition, the active layers of the two regions can be grown at the same time, and selective crystal growth is unnecessary.

[Problem to be solved by the invention]

The conventional example described above has the following problems. First, in the first and second conventional examples, since it is necessary to use selective crystal growth when forming the optical modulator region, manufacturing is difficult and the optical output from the optical modulator is low. Liquid phase epitaxial growth (LPE), vapor phase epitaxial growth (VPE), molecular beam epitaxial growth (MBE), etc. are used for selective crystal growth, but in any of these methods, the DFB laser region and optical modulation Abnormal growth is likely to occur at the border of the organ area.

In addition, since it is difficult to grow uniform semiconductor layer crystals at the boundary, the optical coupling efficiency between the DFB laser region and the optical modulator region is low, ranging from 10% to 50%, resulting in scattering loss of laser light at the boundary. becomes larger, and the optical output from the optical modulator becomes smaller. On the other hand, in the third conventional example,
Since selective crystal growth is not used, manufacturing is relatively easy and a coupling efficiency of nearly 100% can be achieved. However, since the optical modulator utilizes gain change due to current injection, the modulation band is limited to IGHz or less.

The purpose of the present invention is to solve the problems in the conventional example described above, to provide a light emitting device that is easy to manufacture, can achieve optical coupling efficiency close to 100%, and can be modulated at several Gb/s or more. An object of the present invention is to provide a manufacturing method of a semiconductor optical integrated device in which an element and an optical modulator are integrated.

[Means to solve the problem]

The first structure of the semiconductor optical integrated device of the present invention is that a light emitting region and a light modulation region that modulates light emitted from the light emitting region are integrated on one semiconductor substrate, and the light emitting region has a multi-quantum The structure includes an active layer having a well structure, and the light modulation region includes a semiconductor layer having a disordered multi-quantum well structure. Further, in the second structure, a light emitting region and a light modulation region that modulates light emitted from the light emitting region are integrated on one semiconductor substrate,
The structure is characterized in that the light emitting region includes an active layer having a disordered multi-quantum well structure, and the light modulating region includes a semiconductor layer having a multi-quantum well structure. Also,
The manufacturing method of the present invention includes a step of forming a multilayer structure including a multiple quantum well structure on one semiconductor substrate, and a step of introducing impurities into a part of the multiple quantum well structure to disorder the multiple quantum well structure. This manufacturing method is characterized in that the disordered region contains at least two types of impurities, p-type and n-type.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective view showing a first embodiment of a semiconductor optical integrated device according to the present invention, and FIG. 2 is a sectional view taken along line AA' in FIG. This embodiment consists of a DFB laser region 100 and an optical modulator region 200 integrated on one semiconductor substrate. The structural feature is that the DFB laser region 100 has a semiconductor layer (hereinafter referred to as MQWNI) 30 having a multiple quantum well structure.
The modulator region 200 includes a semiconductor layer 40 in which the same multi-quantum well structure (hereinafter referred to as MQW structure) as the active layer is disordered (hereinafter referred to as MQW disordered layer). As is well known, when zero-constant impurities are introduced into a three-layer MQW layer by diffusion or ion implantation, M
The QW structure becomes disordered and changes into a bulk semiconductor layer having an average composition of MQWM30. By appropriately setting the composition and thickness of the three-layer MQW layer and the barrier layer, the MQ
The energy gap of the W disordered layer 40 is
0, which can be slightly larger than the energy of the laser light when used as the active layer of a layered 0FB laser:
When an electric field is applied to the MQW disordered layer 40, the DFB laser light can be modulated by the Franz Keldeitssch effect. Since the MQW disordered layer 40 is logically connected to the original three-layer MQW layer, the optical problem at the boundary between the DFB laser region 100 and the optical modulator region 200, which is a drawback of the conventional example, is There is almost no scattering, and a coupling efficiency close to 100% can be achieved. Therefore, the optical output from the optical modulator region 200 is large.

Hereinafter, the device structure will be explained in detail while following the manufacturing procedure. First, the p-type In with which the diffraction grating 80 is partially formed.
On the P substrate 10, organic metal vapor phase epitaxial growth (
MOVPE), the p-type InGaAsP light guide layer 20. MQW layer three-layer type 0 InP cladding layer 50, n
A type I nGaAsP cap layer 60 is deposited. Here, the MQW layer is composed of a three-layered InGaAs well layer (thickness: 8 nm) with a period of 010 and an InGaAsP barrier layer (photoluminescence wavelength = 1.3 μm, thickness: 11 nm). Next, the DFB laser region 100 is covered with a dielectric film such as a 5i02 film, and the optical modulator region 200 is coated with M from the surface.
Diffusion of sulfur into three QW layers. MQ with sulfur diffused
A buried structure is formed for controlling the zero-order transverse mode, which becomes the MQW disordered layer 40 when the three-layered W layer 0QW structure is broken. First, the DFB laser area 100 and the optical modulator area 2
After etching the central part of 00 into a mesa shape, a high-resistance InP buried layer 90 doped with iron is grown on both sides of the mesa using the MOVPE method. Separation 711300 is formed. Finally, cut out the optical modulator area 2 by cutting out the optical modulator area 2.
A non-reflective coating film 95 is formed on the end face of the semiconductor optical integrated device. The lengths of the DFB laser region 100 and the optical modulator region 200 are 300 μm and 200 μm, respectively.
It is. Furthermore, the wavelength of the DFB laser beam is approximately 1.55. cz
m, the photoluminescence wavelength of the MQW disordered layer 40 with the light modulation region 200 is about 1·45 μm.

FIG. 3 is a sectional view showing a second embodiment of the structure of a semiconductor optical integrated device according to the present invention. This embodiment consists of a DFB laser region 100 and an optical modulator region 200 integrated on one semiconductor substrate. The approximate structure is the first
This is the same as the first embodiment shown in the figure. The structural features of the second embodiment are that, contrary to the first embodiment, the DFB laser region 100 includes an active layer consisting of an MQW disordered layer 41, and the optical modulator region 200 includes one of the three MQW layers. It is to do so. By appropriately setting the composition and thickness of the first layer in the three MQW layers and the barrier layer, the energy gap of one in the three MQW layers can be adjusted to the laser beam of the DFB laser with the MQW disordered layer 41 as the active layer. 1 in the 3 MQW layers of the optical modulator region 200, which can be made slightly larger with respect to energy.
When a field is applied, the DFB laser light can be modulated by the quantum confined Stark effect. The manufacturing procedure is almost the same as the first embodiment, so it will not be described in detail here.

The manufacturing procedure differs from the first embodiment in that in the second embodiment, the region where the MQW structure is disordered by sulfur diffusion is the DFB laser region, and the MQW layer 3 where the crystal grows
The thickness is 1 within the layer. I of 110 periods in 3 layers of MQW layer
The size of the device, which consists of an nGaAs well N (well 7 nm) and an InGaAsP barrier layer (λ, = 1.3 μm, thickness 4 nm), is almost the same as that of the first embodiment. Also DF
The wavelength of the B laser beam is approximately 1.55 μm, and the optical modulation area is 200
The wavelength of one photoluminescence in three MQW layers is approximately 1.4
It is 5 μm.

In the two embodiments described above, since neither structure requires selective crystal growth as used in the conventional example, manufacturing is easy, and the optical connection between the DFB laser region 100 and the optical modulator region 200 is The coupling efficiency is close to 100%, so an optical output of 10 mW or more can be obtained from the optical modulator region 200. In addition, since the Franz Keldysch effect and the quantum confinement Stackle effect are used as the optical modulation method, high-speed modulation of 1 to several Gb/s or more is possible.

In the first and second embodiments, sulfur diffusion was used as a method to disorder the MQW structure, but other methods such as ion implantation may also be used.
It is also possible to use a manufacturing method in which an impurity is added to the QW layer, and then a laser beam is applied only to the region desired to be disordered, and an MQW disordered layer is formed by the heat generated.

In addition to sulfur, zinc or the like can also be used as an impurity to be introduced. However, the semiconductor layer containing sulfur is n
Since a semiconductor layer containing zinc in the mold becomes p-type, the conductivity type of each layer must be set accordingly.

In the following, a method for manufacturing a semiconductor optical integrated device according to the present invention will be explained using FIGS. 4 and 5. The characteristics of this manufacturing method are:
The object of the present invention is to realize an MQW disordered layer with a reduced carrier concentration in manufacturing an optical modulator using the Franz Keldysch effect of the MQW disordered layer as described in the first embodiment.

Generally, to disorder the MQW structure, lQ1gCI
It is necessary to introduce impurities of the order of +-'. For this reason, when the MQW disordered layer is used as an optical modulator as in the first embodiment described above, the carrier concentration of the MQW disordered layer increases, and therefore the operating voltage increases. By using at least two types of impurities, p-type and n-type, as impurities introduced into the MQW layer, the effective carrier concentration of the MQW disordered layer is reduced as a whole by utilizing the compensation effect of the impurities. A manufacturing method is provided.

Figure 4 is a diagram for explaining one embodiment of the manufacturing method of the present invention.The point of the present invention is that MQ has a low carrier concentration.
Since the method for forming the W disordered layer 42 is concerned, FIG. 4 only shows the manufacturing procedure for that part. The manufacturing procedure will be explained below. First, a p-type I on which a diffraction grating 80 is partially formed.
A p-type I layer is formed on the nP substrate 10 by the MOVPE method.
nGaAsP optical guide layer 20, MQW layer 32, n-type In
P cladding layer 50. n-type InGaAsP cap layer 60
(FIG. 4(a)), where an InGaAs well layer (80 m thick) with three MQW layers and a period of 010 is grown (Fig. 4(a)).
and an InGaAsP barrier layer (λ, = 1.3 μm, thickness 11 nm), with a zinc content of about 1018 Cal-'
The doped zero-order DFB laser region 100 is
Covering with a dielectric film 96 such as an i02 film, sulfur is diffused into the optical modulator region 200 from the surface.

In the MQW layer 32 in which sulfur is diffused, the MQW structure is broken and M
By appropriately adjusting the amount of sulfur diffused at this time, the zinc doped during crystal growth is compensated for and the MQW disordered layer 42 becomes the QW disordered layer 42 (Fig. 4(b)). The effective carrier concentration decreases to the order of 10''cm-'.The subsequent method of forming the buried structure is the same as that of the embodiment shown in FIG. 1, so a description thereof will be omitted.

FIG. 5 is a diagram for explaining another embodiment of the manufacturing method of the present invention. The difference from the embodiment of the manufacturing method shown in FIG. 4 is that a light guide layer 21 is formed within the three MQW layers, and sulfur is diffused through this light guide layer. The manufacturing procedure will be explained below. First p
A p-type InP buffer layer 15, an MQW layer 32, an n-type InGa layer are formed on the InP type substrate 10 by MOVPE.
The AsP light guide layer 21 is sequentially grown (FIG. 5(a))
, here, an InGaAs well layer (thickness: 8 nm) with 310 periods in the three MQW layers, and an Ln Ga A sP barrier layer (
The surface dielectric of the 6th order DFB laser region 100 forms a grating 80 in the 0th order DFB laser region 100 doped with zinc to approximately 10 ”on-'. The MQW disordered layer 43 is formed by covering the optical modulator region 200 with M96 and diffusing sulfur into the optical modulator region 200 (FIG. 5(b)). By appropriately adjusting the amount of sulfur diffused at this time, crystal growth is controlled. Zinc doped during the process is compensated for and the effective carrier concentration of the MQW disordered layer 43 is reduced to the order of 1016Cl1-3.
Cladding layer 50. An n-type I n Ga AsP cap layer 60 is sequentially grown (FIG. 5 (C)), and the subsequent method of forming the buried structure is the same as the embodiment shown in FIG. 1.

Note that in the examples of these two manufacturing methods, sulfur diffusion was used as a method for disordering the MQW layered structure, but other methods such as ion implantation may be used.

Also, during crystal growth, two types of p-type and n-type are added to the MQW layer in advance.
It is also possible to use a manufacturing method in which different kinds of impurities are added, and then a laser beam is applied only to the optical modulator region 200 to be disordered, and the MQW disordered layers 42 and 43 are formed by the heat generated.

Above, the structure and manufacturing method of the semiconductor optical integrated device of the present invention have been explained in detail using the semiconductor optical integrated device of the DFB laser and the optical modulator as examples. The present invention can also be applied to optical integrated devices, such as optical integrated devices such as wavelength tunable distributed Bragg reflection type semiconductor lasers and optical modulators. In addition, in terms of crystal growth, VPE
It is also possible to use methods other than the MBE method, for example, the MBE method.

In terms of crystal materials, the present invention is also applicable to semiconductor optical integrated devices using other material systems such as InGaAlAs.

〔Effect of the invention〕

As explained above, the present invention realizes a semiconductor optical integrated device of a light emitting element and an optical modulator that is easy to manufacture and can obtain high optical coupling efficiency by utilizing the disordered structure of the MQW#I structure. It has the effect of In an embodiment in which a DFB laser and an optical modulator are integrated on one semiconductor substrate, one
A semiconductor optical integrated device having a coupling efficiency of nearly 0.00% was obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a first embodiment of the structure of a semiconductor optical integrated device according to the present invention, FIG. 2 is a sectional view taken along line A' in FIG. 1, and FIG. 4 and 5, which are cross-sectional views showing the second embodiment, are diagrams for explaining the method of manufacturing a semiconductor optical integrated device of the present invention. In the figure, 100 is a DFB laser region, 200 is an optical modulator region, 300 is a separation groove, 10 is a substrate, 15 is a buffer layer, 20.21 is a light guide layer, 30, 31, 32.3
3 is an MQW layer, 40°41.42.43 is an MQW disordered layer, 50 is a cladding layer, 60 is a cap layer, 70 is an electrode, 80 is a diffraction grating, 90 is a buried layer, 95 is an anti-reflection coating film, 96 is a dielectric film.

Claims (3)

[Claims] (1) In a semiconductor optical integrated device in which a light emitting region and a light modulation region that modulates light emitted from the light emitting region are integrated on one semiconductor substrate, the light emitting region has a multi-quantum well structure. 1. A semiconductor optical integrated device including an active layer, and wherein the light modulation region includes a semiconductor layer in which the multi-quantum well structure is disordered. (2) In a semiconductor optical integrated device in which a light emitting region and a light modulation region that modulates light emitted from the light emitting region are integrated on one semiconductor substrate, the light emitting region has a disordered multi-quantum well structure. What is claimed is: 1. A semiconductor optical integrated device comprising: a semiconductor layer having a multi-quantum well structure; (3) Reduce the steps of forming a multilayer structure including a multiple quantum well structure on one semiconductor substrate and the step of introducing impurities into a part of the multiple quantum well structure to disorder the multiple quantum well structure. A method for manufacturing a semiconductor optical integrated device, characterized in that the disordered region of the multiple quantum well structure contains at least two types of impurities, p-type and n-type.