JPH08306903A - Semiconductor optical integrated element - Google Patents

Abstract

PURPOSE: To cut down the current expansion for improving the element characteristics such as power consumption efficiency, heat generation, etc., by a method wherein a high resistant and semi-insulating semiconductor substrate is used as a substrate so as to make a region forming an active optoelectronic device of the substrate by implanting impurities to be a dopant for the formation of an active optoelectric device on a conductive layer. CONSTITUTION: Firstly, zinc is selectively diffused in the region forming a photoamplifier and the peripheral electrode so as to form a conductive layer. Later, respective layers of the amplifiers, i.e., a light guide layer 3, an active layer 4, another light guide layer 3, a clad layer 4, another light guide layer 3, a clad layer 5, an electrode layer 6 are formed by successive growing steps. Next, any other parts having the photoamplifier part are removed using photolithographic method and RIE method to form a optical waveguide layer 7 and a clad layer 8 repeatedly leaving the photoamplifier part. Later, an n side electrode 9 and a p side electrode 10 are formed respectively on the electrode contact layer 6 and on the substrate side conductive layer.

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 using a semiconductor, in particular, a passive optical device such as an optical waveguide and an active optical device such as an optical modulator and an optical amplifier are formed on the same substrate. The present invention relates to an integrated optical device.

[0002]

2. Description of the Related Art Conventionally, in an optical integrated device including only an optical device that does not include an electronic device, an n-type or p-type conductive substrate is used as a substrate, and an appropriate metal thin film is attached to the substrate to form an optical integrated device. The structure has been adopted as a common electrode of active optical elements such as optical modulators and optical amplifiers in the above.

[0003]

Problems of the conventional method using the conductive substrate will be described for each type of substrate. First,
When an optical integrated device is manufactured using a p-type substrate, the propagation loss of the optical waveguide increases due to the leakage of light into the p-type substrate that is highly doped, and it is difficult to obtain a high-quality optical integrated device. . Further, since the dopant of the p-type substrate is zinc, which is easy to diffuse, crystal growth at high temperature is difficult. Furthermore, in the conventional structure in which the substrate side is the common electrode,
Since the electrode area on the substrate side is overwhelmingly larger than that on the active optical element side, current spreading occurs when the active optical element is energized, but when the p-type substrate is used, electrons with high mobility are activated. Since the area is determined, there is a big problem that the element characteristics are deteriorated. Therefore, an n-type substrate is generally used in many cases, but in this case, a p-side electrode having a small electrode area (the substrate side is n-type, the active optical element side is
It is difficult to form a mold (especially, InP type), and it is difficult to form a good ohmic electrode. Further, there is a problem of current spreading, though not so much as that of the p-type substrate, and it becomes a problem in terms of power consumption, efficiency, heat generation and the like. Furthermore, these problems become more serious as the degree of integration of optical devices increases. In addition, it may be difficult to integrate active optical elements having different polarities on the same substrate. The present invention has been made in view of the above problems, and is not only an essential solution to current spreading but also has the advantages of using a p-type substrate and the advantages of using an n-type substrate. An object of the present invention is to provide a semiconductor optical integrated device that can realize a structure and is advantageous for high-density integration. Further, according to the semiconductor optical integrated device of the present invention, it becomes extremely easy to integrate active optical devices having different polarities on the same substrate.

[0004]

In order to solve the above-mentioned problems, the present invention uses a semiconductor substrate having a high resistance and a semi-insulating property as a substrate, and a region in which an active optical element is formed on the substrate, or the region and its region. A basic feature is that only the peripheral region is made into a conductive layer by implanting impurities serving as dopants, and an active optical element is formed on the conductive layer to ensure electrical conduction of the active optical element.

[0005]

In contrast to the prior art, the entire substrate side is not made into a conductive layer, but the substrate side is semi-insulating and the region where an active optical element is formed, or only the region and its peripheral region is made into a conductive layer. By doing so, the problem of current spreading can be essentially solved. As a result, power consumption, efficiency, heat generation, etc. can be significantly improved. Further, if the conductive layer is of p-type, the upper electrode on the active optical element side can be formed of n-type, so that an ohmic electrode can be easily formed (advantage when using a p-type substrate) and at the same time, an optical waveguide. Since the substrate-side clad has a semi-insulating property, a good optical waveguide can be formed also in terms of propagation loss (advantage when using an n-type substrate).
The conductive layer can be easily formed by a conventional method such as selective diffusion or ion implantation.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a semiconductor optical integrated device of the present invention in which an optical waveguide as a passive optical device and an optical amplifier as an active optical device are integrated on the same substrate will be described with reference to FIG.
FIG. 1A is a plan view showing an outline of the semiconductor optical integrated device, and FIG. 1B is a sectional view taken along the line AA ′ in FIG. Each layer of the optical waveguide and the optical amplifier is formed by the following steps. First, semi-insulating indium phosphide (InP)
In the substrate 1, zinc is selectively diffused into a region where an optical amplifier is formed, its peripheral portion and a region 2 where an electrode on the substrate side is formed to form a conductive layer. After that, each layer of the optical amplifier, that is, undoped InGaAsP (bandgap wavelength λg =) is formed by MOVPE method (metal organic chemical vapor deposition method).
1.15 μm) Optical guide layer 3, undoped In Ga As
P (λg = 1.3 μm) active layer 4, undoped In Ga
As P (λg = 1.15 μm) Optical guide layer 3, n-In
P clad layer 5, n ⁺ -In Ga As P (λg = 1.3
μm) The electrode contact layer 6 is sequentially formed by epitaxial growth. Next, by using the photolithography method and the RIE method (reactive ion etching method), the optical amplifier portion is left and the others are removed, and the MOVPE method is used again.
An undoped InGaAsP (.lambda.g = 1.15 .mu.m) optical waveguide layer 7 and an n-InP cladding layer 8 are formed by epitaxial growth. After forming the optical waveguide and the optical amplifier, an n-side electrode 9 is formed on the electrode contact layer 6 of the optical amplifier, and a p-side electrode 10 is formed on the conductive layer on the substrate side, as shown in FIG. . The optical integrated device of the present invention has a wavelength of 1.3.
After passing a signal light of .mu.m, the propagation loss of the optical waveguide was 0.
Good characteristics of 3 db / mm were obtained and the operation of the optical amplifier was also good.

As another embodiment of the present invention, an example in which an optical waveguide and an optical switch are integrated to form a current injection type total reflection type optical switch will be described with reference to FIG. Figure 2
FIG. 3A is a plan view showing an outline of a 1 × 2 total reflection type optical switch. When there is no current injection, the input light goes straight and is output to the optical output 1. When a current is injected from the p-side electrode 18, the refractive index of the lower region of the electrode 11 changes and functions as a light reflecting mirror, so that the input light is totally reflected and output to the light output 2. 2B is a sectional view taken along line BB ′ of FIG. An undoped AlGaAs clad layer 13 is formed on the semi-insulating gallium arsenide (GaAs) substrate 12 by epitaxial growth using the MBE method (molecular beam epitaxy method). Next, zinc is selectively diffused into the region 14 including the region corresponding to the current injection part of the optical switch and the electrode forming part. It is important that the zinc diffused at this time is sufficiently diffused also in the GaAs substrate 12. Then MB again
Undoped GaAs optical waveguide layer 15, n-AlG by E method
The aAs clad layer 16 and the n ⁺ -GaAs electrode contact layer 17 are formed by epitaxial growth. The switch shape shown in FIG. 2A is formed by using the photolithography method and the RIE method, and finally, the n-side electrode 11 and the p-side electrode 18 are formed.
To form. In the case of the present embodiment, by forming a conductive layer also in a part of the layers constituting the active optical element, the current can be efficiently and intensively injected into the region below the electrode 11. According to the present embodiment, the switching current is about 1 as compared with the case where the optical element having the same structure is formed on the p-type substrate.
I was able to set it to / 3.

[0008]

The semiconductor optical integrated device of the present invention can reduce the current spreading, which is a problem when a conventional conductive substrate is used, by using a high-resistance and semi-insulating substrate, thereby reducing power consumption and efficiency. The element characteristics such as heat generation can be remarkably improved. Further, by limiting the conductive region to the region where the active optical element is formed, or the region and its peripheral region, a low loss optical waveguide can be manufactured. Furthermore, if the substrate side is a p-type, an optical integrated device in which contact electrodes can be easily manufactured can be formed, and it is also advantageous in improving the degree of integration, so that a highly functional and small optical integrated device can be realized. Furthermore, active optical devices having different polarities can be easily integrated on the same substrate.

[Brief description of drawings]

FIG. 1A is a plan view showing an outline of an embodiment of an optical integrated device of the present invention in which an optical waveguide and an optical amplifier are integrated,
9B is a sectional view taken along line AA ′ of FIG.

2A is a plan view showing an outline of another embodiment of the optical integrated device of the present invention configured as a total reflection type optical switch, and FIG. 2B is a sectional view taken along line BB ′ of FIG. 2A. Fig.

[Explanation of symbols]

1 Semi-insulating InP substrate 2 Zinc selective diffusion region 3 Undoped InGaAsP (λg = 1.15 μm)
Optical guide layer 4 Undoped InGaAsP (λg = 1.3 μm) active layer 5 n-InP clad layer 6 n + -InGaAsP (λg = 1.3 μm) electrode contact layer 7 Undoped InGaAsP (λg = 1.15 μm)
Optical waveguide layer 8 n-InP clad layer 9 n-side electrode 10 p-side electrode 11 n-side electrode 12 semi-insulating GaAs substrate 13 undoped AlGaAs clad layer 14 zinc selective diffusion region 15 undoped GaAs optical waveguide layer 16 n-AlGaAs clad layer 17 n + -GaAs electrode contact layer 18 p-side electrode

Claims (2)

[Claims] 1. A semiconductor optical integrated device in which an active optical device and a passive optical device are integrated and formed on the same substrate, and electronic devices are not integrated on the same substrate. In the semiconductor optical integrated device, a high resistance and semi-insulating semiconductor is provided on the substrate. A substrate is used, and a region of the substrate where an active optical element is formed, or only the region and its peripheral region is made into a conductive region by implanting an impurity serving as an n-type or p-type dopant, and the region is A semiconductor optical integrated device, characterized in that it is a conductive region on the substrate side of an active optical device. 2. A semiconductor optical integrated device in which an active optical device and a passive optical device are integrated and formed on the same substrate, and electronic devices are not integrated on the same substrate. In the semiconductor optical integrated device, a high resistance and semi-insulating semiconductor is provided on the substrate. A substrate is used, and a region of the substrate in which the active optical element is formed and a part of a layer forming the active optical element, or only the region and its peripheral region, are provided with an n-type or p-type dopant. A semiconductor optical integrated device characterized in that a conductive region is formed by implanting the impurity, and the region is used as a conductive region on the substrate side of the active optical device.