JPH0364077A - Long wavelength avalanche photodiode - Google Patents

Abstract

PURPOSE:To obtain a long wavelength avalanche photodiode-(APD) which can be simply formed with a guard ring and has a uniform multiplication factor in a photodetector by employing a transparent electrode forming a Schottky junction together with n-type InP as a surface electrode. CONSTITUTION:A guard ring region 8 by a shallow Be ion implantation is formed to suppress edge breakdown at the edge of a Schottky electrode, and a transparent electrode 12 for forming a Schottky junction with an n-type InP multiplying layer 5 is formed on a photodetector. Its periphery is surrounded by an insulating protective film 7, and a surface ohmic electrode 10 in ohmic contact with the electrode 12 is formed thereon. Since this APD structure is of Schottky type, it is not necessary to form a Cd diffused (P<+>-type) region, and a guard ring can be simply formed. Since the transparent electrode is used, a distribution of uniform multiplication factor is obtained in the photodetector similarly to a conventional APD.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a long-wavelength avalanche photodiode (
(hereinafter abbreviated as APD) structure.

[Conventional technology]

Figure 2 is a cross-sectional view showing the structure of a conventional long-wavelength APD.
s or (indicated by / below) rnGaAsP light absorption layer,
(4) is n-TnGaAs to improve frequency response.
P layer, (6) is n-, InP multiplication layer, (6) is n--I
nP gadling layer, (7) is a protective insulating film, (8) is B
E is a guard ring region formed by ion implantation, (9) is a Cd diffusion region, 01 is a front surface ohmic electrode, and αD is a back surface ohmic electrode.

Next, a method of manufacturing a conventional long-wavelength APD full structure will be explained. On n''-InP substrate +11, n--InP banff 1 layer (2), n--1nGaAs/InGaAsP light absorption layer (3), n--1nGaAsP layer (4), n-I
nP multiplication layer (5), n--InP garrison layer (6)
Sequentially conduct epitaxy. Thereafter, by Be ion implantation and annealing, a guard ring region (8) having a P''nl oblique junction with a small concentration gradient and a Cd diffusion region (9) forming a P'' step junction are formed.

Finally, the front ohmic electrode α and the back ohmic electrode α
A long wavelength APD structure is fabricated based on D.

Next, the operating principle of the long wavelength APD structure will be explained.

Long-wavelength light enters the light-receiving surface surrounded by the ring-shaped surface electric ivy electrode Ql, and passes through the protective insulating film (7), the CD diffusion region +9), the n-InP multiplication layer (5), and the n-InP multiplication layer (5). -InGa
Each layer of the AsP layer (4) is efficiently transmitted, and all n--1
It is absorbed by the nGaAs/I nGaAs P light absorption layer (3) and generates carrier pairs by photoexcitation.

Between the front ohmic electrode αφ and the back ohmic electrode Oυ, there is always a reverse voltage on the verge of causing avalanche breakdown in the multiplication region, which is the n-InP multiplication layer (5) under the Cd diffusion region (9). is applied,
The depletion layer extends sufficiently to the n--1nGaAs/InGaAsP light absorption layer (3). n-I n G a A
Carrier pairs generated in the S/InGaAsP light absorption layer (3) drift due to the electric field applied to this depletion layer. In this case, holes are injected into the multiplication region, and the high electric field ionizes the atoms in rnP in an avalanche manner, multiplying the holes by avalanche. The generation of multiplication carriers is almost completed in the time it takes for carriers to pass through the multiplication region, so there is little excess noise, multiplication of small signals, and high-speed response can be obtained. Therefore, the combination of conduction types shown in Figure 2 is used.

[Problem to be solved by the invention]

Conventional long-wavelength APDs are configured as described above, so the formation of the Cd diffusion (P'') SN region is one of the important processes that determines the characteristics of the APD, and reliable controllability is desired. . Furthermore, since the guard ring region is formed to sufficiently include the edge of the diffusion front formed by the Cd diffusion region, reliable controllability is desired. However, in both processes, the controllability was difficult. The present invention was made to solve the above-mentioned problems, and aims to provide an APD in which the guard ring region is easy to form and has a uniform multiplication factor in the light receiving section.

[Means to solve the problem]

I n Ga As / T n according to this invention
The APD structure of G a A s P has n as a surface electrode.
-It is a Schottky type APD structure using InP and a transparent electrode that forms a Schottky junction.

[Effect]

In this invention, the Schottky type APD structure using a transparent electrode that forms a Schottky junction with n-InP is a Schottky type, so there is no need to create a Cd diffusion (P'') fil region, and a guard ring is used. Formation of the region is also simple.Furthermore, since a transparent electrode is used, a uniform distribution of the multiplication factor can be obtained in the light receiving section, similar to the conventional APD.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows Schottky-type InGaAs/I using n-InP and a transparent electrode to form a Schottky junction.
FIG. 2 is a cross-sectional view showing the APD structure of nGaAsP. In the figure, i11~<51, +71, +8
1, α0. αD is equivalent to that shown in the conventional example of FIG.

Next, the operation will be explained. n”InP substrate +1! On top of that, n--InP buffer layer (2), n--InGaA
sPn--InGaAsP light absorption layer (3), n-InG
The formation of the epitaxial layers of the aAsP layer (4) and the n-InP multiplication layer (5) is the same as that shown in the conventional example of FIG.

In the manufacturing method according to the present invention, in order to suppress edge breakdown at the edge portion of the soft key electrode,
A guard ring 9N region (8) is formed by ion implantation,
A transparent electrode αυ that forms a Schottky junction with the n-Inp multiplier N(5) is formed on the light receiving section.

It is surrounded by an insulating protective film (7), and a transparent t-shirt is placed on top of it.
Create a surface ohmic electrode OI that makes ohmic contact with sia.

〔Effect of the invention〕

As described above, according to the present invention, since it is a Schottky type, there is no need to create a Cd-diffused (P") SN region, and the formation of the guard ring 9N region is easy. Also, since a transparent electrode is used, , in the light receiving section like the conventional APD,
This has the effect that a uniform distribution of multiplication factors can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a long wavelength APD according to an embodiment of the present invention, and FIG. 2 is a sectional view showing the structure of a conventional long wavelength APD. In the figure, (1) is an n''-InP base layer, (2) is an n--InP buffer layer, and (3) is an n--
TnGaAs/InGaAsP light absorption layer, (4) is n-
-InGaAsP layer, (5) is n-InP multiplication layer, (7
) is a protective insulating film, (8) is a guard ring region, HO is a front ohmic electrode, GO is a back ohmic electrode, and (2) is a transparent electrode. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A long wavelength avalanche photodiode characterized in that a transparent electrode forming a Schottky junction with n-InP is used as a surface ohmic electrode.