JPS62194684A - Semiconductor light-receiving device - Google Patents

Abstract

PURPOSE:To lessen a dark current of a light-receiving device by a method wherein a pair of metal electrodes containing impurities of one conductivity type, which are formed on a semiconductor layer of the other conductivity type connected on a substrate, are alloyed to form a horizontal-type alloyed transistor structure. CONSTITUTION:The device is constructed in such a manner that, an SI-GaAs substrate 1 being used as a substrate, alloy barriers are formed by paired metal electrodes 5 and 6 on an n-GaAs layer 2 of thickness 3mum, a semiconductor layer (light-absorbing layer), connected on the substrate. The metal electrodes 5 and 6 are alloyed respectively by a method wherein a gold zinc (AuZn, Zn 5%) layer of thickness 2,000Angstrom having fifteen comb teeth of width 3mum disposed at an interval of 9mum is heated at 450 deg.C for 3min. The metal electrodes 5 and 6 are so disposed as to be spaced at 3mum from each other.

Description

Detailed Description of the Invention [Summary] MSN-PD (Me
tal-Semiconductor-Metal P
By developing a structure in which a photodetector is made into a lateral transistor by alloying or diffusion, the dark current of the photodetector can be reduced.

[Industrial application field]

The present invention relates to a semiconductor light receiving device. This invention relates to a structure that is an improved version of lSM-PD.

Conventional photodetectors use PIN (p-type semiconductor-insulating layer-n-type semiconductor) diodes and AI'D (Avala diode).
Elements with a bulk structure, such as photodiodes (photodiodes), were often used.

On the other hand, MSN-PD is a surface-structured device, which has a simple structure and is easy to integrate. For example, field effect transistor (FE)
When integrating with T), MS is applied at the same time as gate metal evaporation.
It has advantages such as being able to form an M-PD.

However, MSN-PDs have drawbacks in that it is difficult to form a Schottky barrier and dark current tends to be large compared to the above-mentioned bulk structure elements, and improvements are desired.

[Conventional technology]

Figure 5 (1) and (2) are respectively 0 and 8μ according to the conventional example.
FIG. 2 is a cross-sectional view and a plan view of an m-band MSM-PD.

In Fig. 5 1)), semi-insulating gallium arsenide (Sl-
n-type GaAs) as a light absorption layer deposited on the substrate 1
s (n-GaAs) layer 2 and aluminum (eight electrode 3.
The MSM-PD is constructed by forming a Schottky barrier in step 4.

In FIG. 5(2), the AI electrodes 3 and 4 are each formed in a comb shape, with teeth intertwined alternately.

FIG. 5(1) shows the AA cross section.

As described above, the comb-shaped structure of the electrodes provides a large light-receiving area.

Figure 6 shows a conventional MSM in the 1, 3 to 1.6 μm band.
It is a sectional view of PD.

In the figure, indium gallium arsenide (INO,
s:+Gao, =7As) layer 12 and At electrode 13.
The MSM-PD is constructed by forming a Schottky barrier in step 14.

[Problem that the invention seeks to solve]

Conventional MSM-PD has a low Schottky barrier height,
Dark current is large.

In particular, it is difficult to form a Schottky barrier in InP-based semiconductors.

[Means for solving problems]

The solution to the above problem is to create a semiconductor photodetector device that has a horizontal alloy transistor structure by alloying a pair of metal electrodes containing impurities of the other conductivity type on a semiconductor layer of one conductivity type deposited on a substrate, or This is achieved by forming a pair of impurity-introduced regions of the other conductivity type in the deposited semiconductor layer of one conductivity type, and forming a metal electrode on the regions to form a semiconductor light receiving device having a lateral diffusion transistor structure.

[Effect]

FIG. 3 is an energy level diagram of a conventional MSN-PD.

As shown in the figure, since the MSN-PD uses a Schottky barrier in the junction, the barrier heights φ7 and φ of the electrodes (anode and cathode), which affect the dark current, are smaller than the forbidden band width E of the semiconductor layer. is also small, approximately (1/2)E.

FIG. 4 is an energy level diagram of a light receiving device having a lateral transistor structure according to the present invention.

In this case, when the lower end of the conduction band of the semiconductor is adjusted to the Fermi level, the barrier height φ7, φ= of the alloy or diffusion junction that influences the dark current is approximately equal to the forbidden band width E9 of the semiconductor layer.

In this way, in the present invention, the barrier height is increased and the dark current is lower than that of the conventional one. It can be reduced compared to ISM-PD.

Note that diffusion bonding is more effective in reducing dark current than alloy bonding in terms of bonding integrity.

〔Example〕

FIG. 1 is a sectional view of a light receiving device having a 0.8 μm band horizontal alloy transistor structure according to the present invention.

In the figure, a 5l-GaAs substrate 1 is used as the substrate,
The thickness of the semiconductor layer (light absorption layer) deposited on it is 3 μm
An alloy barrier is formed on the n-GaAs layer 2 by a pair of metal electrodes 5.6.

Each of the metal electrodes 5.6 is 1 as shown in FIG. 5(2).
Five comb teeth with a width of 3 μm arranged at a spacing of 9 μm.
2000 gold zinc (AuZn, Zn5%) layers 45
Alloy by heating at 0°C for 3 minutes.

The metal electrodes 5.6 are arranged at a mutual interval of 3 μm.

FIG. 2 is a sectional view of a light-receiving device having a lateral diffusion transistor structure in the 0.8 μm band according to the present invention.

In the figure, an n-GaAs layer 2 with a thickness of 3 μm is deposited on a 5l-GaAs substrate 1, and a diffusion barrier is formed by a pair of p-type impurity doped regions 7.8.

Each p-type impurity-introduced region 7.8 is a zinc (Zn) diffusion layer with a depth of 0.5 to 1 μm formed with 15 comb teeth each having a width of 3 μm and an interval of 9 μm, as shown in FIG. 5(2). It is.

The p-type impurity introduced regions 7.8 are arranged at a mutual interval of 3 μm.

Zn diffusion was performed using a patterned silicon nitride (Si3N4) layer with a thickness of 500 to 600 nm as a mask.
Perform at °C.

AuZn electrode 9.10 on p-type impurity introduced region 7.8
form.

The dark current of a conventional MSM-PD was about 100/JA, but in the above embodiments it was one to two orders of magnitude smaller than this.

In the embodiment, GaAs is used for the semiconductor layer, but other semiconductor layers such as InGaAs% aluminum indium arsenide (^l InAs) may be used instead.

〔Effect of the invention〕

As explained above, according to the present invention, the dark current of the light receiving device is reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a light receiving device with a lateral alloy transistor structure in the 0.8 μm band according to the present invention. FIG. 2 is a cross sectional view of a light receiving device with a lateral diffused transistor structure in the 0.8 μm band according to the present invention. FIG. 4 is an energy level diagram of a conventional MSM-PD, FIG. 4 is an energy level diagram of a light receiving device with a lateral transistor structure of the present invention, and FIGS. 5 (1) and (2) are 0 and 8μ according to the conventional example, respectively
A cross-sectional view and a plan view of an m-band MSM-PD.
It is a sectional view of PD. In the figure, l is the substrate, which is a 5l-GaAs substrate, 2 is a semiconductor layer of one conductivity type, which is an n-GaAs layer, 5.6 is a metal (AuZn) electrode, and 7.8 is an impurity introduction region of another conductivity type, where p-type impurities are introduced. Area, 9, IO is a dispute over the drawing of a metal (AuZn) electrode $5 (no change in π) Procedural amendment □ Drafted in 061 - No. 36261 2, Name of the invention Semiconductor photodetector device 3, Relationship with the case of the person making the amendment Patent applicant address 1015 Kamiodanaka, Nakaatsu-ku, Yozaki City, Kanagawa Prefecture (5
22) Name: Fujitsu Limited 4, Agent Address: 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited) As per il1 company

Claims (2)

[Claims] (1) A semiconductor light-receiving device characterized by comprising a semiconductor layer of one conductivity type deposited on a substrate and a pair of metal electrodes containing impurities of the other conductivity type alloyed together. (2) A semiconductor light-receiving device characterized in that a pair of impurity-introduced regions of the other conductivity type are formed in a semiconductor layer of one conductivity type deposited on a substrate, and an electrode is formed on the regions.