JPH0758806B2 - Optical semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device having a light receiving element and a light emitting element formed of a semiconductor.

2. Description of the Related Art Conventionally, a semiconductor light-receiving element for optical communication and a light-emitting element are individually configured as a light-receiving device and a light-emitting device. For example, in the case of light receiving elements, Si-PIN photodiodes are used for short wavelengths, and Ge or InGaAs-PIN photodiodes are used for long wavelengths.
AlAs light emitting diode (LED), InGaAsP-LED for long wavelength
Is mainly used. In the case of data transmission, the modulated light incident from the light emitting element is propagated through the optical fiber and is received by the light receiving element. Therefore, in bidirectional data transmission in which transmission and reception are performed, at least two sets of the above system, that is, two sets each including a light emitting element, a light receiving element, and an optical fiber are required. Further, when bidirectional data transmission is performed with one optical fiber, there is a demultiplexer installation and attendant input / output attenuation.

Therefore, an optical semiconductor device having a structure in which the light receiving element and the light emitting element are present in one package and the center axis of the light receiving surface of the light receiving element and the center axis of the light emitting diameter of the light emitting element coincide with each other has been realized. This is because the light receiving area and the light emitting area are close to each other, so that if the element is installed at the position of the maximum output of the fiber end, the maximum light receiving sensitivity can be obtained, and the maximum output of the fiber end can be obtained at the same position without realigning the optical axis. Maximum light receiving sensitivity can be obtained. Therefore, bidirectional data transmission becomes possible without using a demultiplexer with a single optical fiber.

In the light emitting element section of this optical semiconductor device, in order to efficiently guide the light from the counter-installed fiber to the light receiving surface of the lower light receiving element section, a part of the metal electrode on the front surface and the adhesive surface is received by the light receiving element section. It is removed near the central axis that coincides with the central axis of the surface, and its diameter is made larger than the fiber diameter.

On the other hand, the light emitting area of the light emitting element section must be smaller than the core diameter of the fiber in order to make the center axis of the light emitting diameter substantially coincide with the center axis of the light receiving surface of the light emitting element section and to efficiently couple with the fiber. . For this reason, bidirectional data transmission is possible without using a demultiplexer with a single optical fiber.

In the light emitting element section of this optical semiconductor device, in order to efficiently guide the light from the oppositely installed fiber to the light receiving surface of the lower light receiving element section, a part of the metal electrode on the surface and the adhesive surface is It is removed near the central axis that coincides with the central axis of the light-receiving surface, and its diameter is made larger than the fiber diameter.

On the other hand, the light emitting area of the light emitting element section must be smaller than the core diameter of the fiber in order to make the center axis of the light emitting diameter substantially coincide with the center axis of the light receiving surface of the light emitting element section and to efficiently couple with the fiber. . Therefore, it is necessary to use a reverse bias current confinement structure and to provide a path for conducting a current from the metal electrode to the light emitting region. As this method, a thermal diffusion method using an element such as zinc, an ion implantation method, or another method is used.

However, in the above conventional configuration, the incident light from the optical fiber is transmitted through the inside of the light emitting element and reaches the light receiving surface of the light receiving element installed in the lower portion, so that in each layer forming the light emitting element. Most of the light is absorbed, and the incident light that contributes to the reception of light is significantly attenuated. In order to reduce the absorption of this incident light, it has been confirmed by experiments that the light receiving sensitivity is improved by thinning the active layer, which is the part where the absorption is remarkable. However, the double hetero structure currently commercialized As compared with the film thickness (1-1.5 μm) of GaAlAs-LED, there are some in which the change in light output with time is observed, which causes a decrease in reliability.

For this reason, it is necessary to reduce the proportion of incident light absorbed inside the light emitting element without changing the thickness of the active layer.

An object of the present invention is to reduce absorption of incident light in a light emitting device without impairing reliability, and thereby improve light emission sensitivity.

Means for Solving the Problems The optical semiconductor device of the present invention has a semiconductor light-emitting element on the main surface of the semiconductor light-receiving element, which is attached to the main surface of the semiconductor light-receiving element such that the central axes of the light-emitting diameters are aligned. A p-type inversion region (hereinafter referred to as a p ⁺ layer) is formed on the formed n-type region, and the p-type inversion region is formed on at least a part of the light receiving surface of the light receiving element.
This structure has a selection region in which the type inversion region is not formed.

In the case of the conventional light emitting device, the incident light from the fiber end is not only the absorption of the active layer, but also the high concentration p ⁺ layer is a major factor of the absorption of the incident light. The main function of the present invention is to selectively form this p ⁺ layer and
By preventing the absorption in the p ⁺ layer and reaching the light receiving surface of the light receiving element, it contributes to the improvement of the light receiving sensitivity.

EXAMPLE An example of the optical semiconductor device of the present invention will be described with reference to the sectional view shown in FIG.

In FIG. 1, an insulating film 9 is formed on the semiconductor light receiving element B,
The principal part sectional drawing of one Example of the structure which bonded the semiconductor light receiving element A is shown. By providing this insulating film 9, the light receiving element B and the light emitting element A are electrically separated, and both the light receiving and light emitting functions can be used independently. In the embodiment of the present invention,
As an example, a semiconductor device integrated with light receiving and emitting by using a combination of a Si light receiving element and a GaAlAs / GaAs light emitting element is used.

In the structure of the PIN photodiode as the semiconductor light receiving element B, a high resistance i (n) layer 2 is formed (phosphorus is used for doping) on an n-type Si substrate 1, and a p layer 3 is formed therein. It is formed by diffusion. A guard ring 5 is provided around the light receiving region by boron diffusion. Light receiving surface is 0.15 mm
With φ, the structure is such that the channel stopper region 4 is formed around the guard ring 5 by phosphorus (P) diffusion.

The structure of the GaAlAs-LED as the semiconductor light emitting device A is as follows: n ₀ -GaAlAs substrate layer 12, n ₁ -GaAlAs confinement layer 13, p ₁ -GaAs active layer 14, p ₂ -GaAlAs confinement layer 1
The 5, n ₂ -GaAlAs current confinement layer 16 was continuously formed by a normal liquid phase epitaxial growth method, and then the n-type GaAs substrate was removed by selective etching.

After that, a recess having a diameter of 40 μm (the core diameter of the fiber used is 110 μm) was formed in the current confinement layer n ₂ —GaAlAs 16 by selective etching. The surface of the n ₂ -GaAlAs layer 16 is selectively diffused with a mask of SiO ₂ into a portion where a p-type electrode is vapor-deposited, a concave portion, and a current introduction portion to change to a p-type and a concave portion.
A p ⁺ region 17 is formed in the p ₂ -GaAlAs layer 15, and a p-type electrode 18 having a diameter larger than the diameter of the fiber light emitted from the fiber to the upper portion of the light emitting element is vapor-deposited on the p ⁺ region 17.
A recess is formed in the n-side electrode 10 so as to match the light extraction window of the upper light emitting element, and a window having a diameter larger than the light receiving diameter of the lower portion is opened. A microsphere lens is mounted on the top of the chip to narrow down the emission beam and incident light.

With such a structure, the light incident between the p-type electrode and the recess reaches the light receiving surface without being absorbed by the p ⁺ layer 17, and contributes to the improvement of the light receiving sensitivity. Therefore selected diffused p ⁺ layer 17 Ga
The photosensitivity of the Si-PIN photodiode with AlAs-LED bonded on top was about 0.18A / W, which is more than 10% higher than 0.16A / W without selective diffusion.

In the embodiments of the present invention, the Si light receiving element and the GaAlAs / GaAs light emitting element are shown as examples, but it goes without saying that the same effect can be obtained even when other materials such as the InGaAs light receiving element and the IsP light emitting element are used. Further, in forming the p-type inversion region, the same effect can be obtained even when other means such as ion implantation is used instead of thermal diffusion.

According to the optical semiconductor device of the effects The present invention conventionally by p ⁺ incident light which has been absorbed in the diffusion layer is selectively diffused p ⁺ diffusion layer, without being absorbed in the p ⁺ diffusion layer, It reaches the light receiving surface of the light receiving element and contributes to the improvement of the light receiving sensitivity.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor light receiving device showing an embodiment of an optical semiconductor device of the present invention. A: semiconductor light emitting element, B: semiconductor light receiving element, 1 ...
n-type Si substrate, 2 ...... high-resistance i (n ^-) layer, 3 ...... p ⁺ diffusion layer, 4 ...... channel stopper, a guard ring with 5 ...... boron diffusion, 6 ...... p-side electrode (PD), 7 ... oxide film,
8 ... n-side electrode (PD), 9 ... insulating film, 10 ... n-side electrode (LED), 11 ... antireflection film, 12 ... n ₀ -GaAlAs substrate layer, 13 ... n ₁ -GaAlAs Confinement layer, 14 …… p ₁ -GaAs active layer, 15 …… p ₂ −GaAlAs confinement layer, 16 …… n ₂ −GaAlAs current confinement layer, 17 …… p ⁺ selective diffusion layer, 18 …… p side electrode ( LE
D), 19 ... Non-diffused part, 20 ... Current introduction part.

Claims (1)

[Claims] 1. In an optical semiconductor device bonded to the center axis of the light receiving surface of a semiconductor light receiving element such that the center axes of the light emitting diameters of the semiconductor light emitting elements coincide with each other, the main surface of the light emitting element bonded to the light receiving element. A p-type inversion region is formed by adding a p-type impurity to the n-type region formed in the above, and the p-type inversion region is not formed in at least a part of the region located on the light receiving surface of the light receiving element. An optical semiconductor device having a region.