JPH0215680A - Semiconductor photodetecting device - Google Patents

Abstract

PURPOSE:To decrease a mesa-type photodetecting element in a dark current and to improve it in reliability by a method wherein the side face of a mesa is made semi-insulated by the introduction of an inert impurity. CONSTITUTION:The following are successively grown on an n-type InP substrate 31 through an MOCVD method: an n-type InP buffer layer 32; an n-type InGaAs light absorbing layer 33; an n-type InGaAsP barrier alleviating layer 34; an n-type InP electrical field alleviating layer 35; and an n-type InP layer. After that, the uppermost InP layer is made to serve as an n-type InP multiplying layer 36 and a p-type InP layer 37 though the diffusion of Zn 2mum in depth to form a p-n junction 38. After a protecting film 39 has been formed on a side face of a mesa, oxygen is introduced through an ion implantation for the formation of a semi-insulating region 40. Next, the substrate 31 is annealed at a temperature of 700 deg.C, and then a p-electrode 41 and an n-electrode 42 are built to form an APD.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor light receiving device, and particularly to the structure of an avalanche photodiode (hereinafter abbreviated as APD) having a mesa structure and a pin photodiode, and a manufacturing method thereof.

[Conventional technology]

In the following, an InP-based light receiving element will be explained as an example.

In APD, covering the main joint end is an important issue. In a planar APD, a guard ring junction is formed to cover the main junction curved portion. However, controlling the depth of the guard ring junction is extremely difficult. In other words, subtle differences in the relative position of the guard ring junction depth and the main junction depth and the distance to the light absorption layer make a big difference in APD characteristics, and considering the thickness variation of the epitaxial layer, control is difficult. Very difficult. In this respect, since there is no curved part of the APD main junction of the mesa type structure, there is an advantage that no guard ring junction is required.

For example, Electronics Letters (ELECTRONIC3LETTER5) No. 29, 9
The conventional structure is shown in FIG. 2. In the same figure, 11 is p-type I
nP substrate, 12 is a p-type InP layer, 13 is an n-type InP layer,
14 is an n-type InGaAs P layer, 15 is an n-type InGaAs layer (light absorption layer), and 16 is a p electrode.

17 is an n electrode, and 18 is a pn junction. but,
As you can see from the figure, the mesa-shaped structure.

The ends of the pn junction 18 and the light absorption layer 15 are exposed on the side surface of the mesa, making it difficult to protect them, resulting in a disadvantage in terms of reduction in surface leakage current and reliability.

In addition, the mesa-type structure is a pin photodiode (hereinafter referred to as a pin photodiode).
For example, the conventional example shown in Figure 3 is Electronics Letters (HLECTRON).
IC5LETTf! R3) 9th, May, 2nd 1985
This is the structure of Volume 1, No. 10, pages 441-442. In the same figure, 21 is an n-type InP substrate, 22 is an n-type InP substrate, and 22 is an n-type InP substrate.
layer, 23 is an n-type InGaAs layer (light absorption layer)
, 24 is a p-type I n Ga As layer, 25 is a p-type I
nP layer, 26 is p electrode, 27 is pn junction 0
In this example as well, the ends of the pn junction 27 and the light absorption layer 23 are exposed on the side surface of the mesa, which has the same drawback as the conventional example shown in FIG.

[Problem to be solved by the invention]

The above-mentioned conventional technology for the mesa structure photodetector does not take into consideration the protection of the pn junction end and the light absorption layer end exposed on the side surface of the mesa, and problems remain in terms of surface leakage current reduction and reliability. Ta.

An object of the present invention is to eliminate the above-mentioned drawbacks of mesa-type structures.

Incidentally, an example in which a SiN film is deposited on the side surface of the mesa (for example).

There is also a Proceedings of the 1981 IEICE Semiconductor and Materials Division National Conference 314), but it is considered insufficient in terms of reliability.

[Means to solve the problem]

Means for achieving the above object will be explained using FIG. 1 using an APD as an example. In FIG. 1, 1 is an n-type InP substrate, and 2 is an n-type InGaAs light absorption layer.

3 is an n-type InP multiplication layer, 4 is a p-type InP layer, and 5 is a pn
It is a joining. 6 is achieved by introducing inert impurities into the above 1 to 6.
5 is a semi-insulating region, 7 is an insulating film, 8 is a p-electrode, 9
is an n-electrode.1 The purpose of the present invention is to protect the side surfaces of the mesa.
This is achieved by introducing inactive impurities into the semiconductor region 6 which has been made into a semi-insulator.

[Effect]

By introducing inert impurities into the mesa side surfaces to make them semi-insulating, the end faces of the pn junction 5 and the light absorption layer 2 are no longer exposed to the semiconductor crystal ends, suppressing surface leakage current and improving reliability. A good APD can be produced.

The effect of the present invention is that, as described above, p
The purpose of this method is to confine the n-junction end and the light absorption layer end, and is essentially different from methods such as depositing an insulating film on the mesa side surfaces or burying the mesa portion with semi-insulating semiconductor crystal. In other words, in the method of depositing or embedding an insulating film on the mesa side surface, the interface between the mesa side surface and the deposit or buried layer is active, and methods other than the present invention cause contamination of this interface or introduction of active impurities. This is because it is easy.

〔Example〕

Example 1 This will be explained using FIG. 4. On an n-type InP substrate 31 (S-doped t n = I
Type InP buffer layer 32 (undoped, 0.5pm)
, n-type InGaAs light absorption layer 33 (undoped, 2 μm
), n-type InGaAsP barrier relaxation layer 34 (undoped,
Q, 2 μm) m n-type InP electric field relaxation layer 35 (Si doped, n=2X10"m""81.2 μm), n-type InP
A layer (undoped, 2.6 μm) was continuously grown using MOCVD. The carrier concentration of the undoped layer is 1 to 5X
It was 101Bam-8. After this, Zn at a depth of 2 μm
By diffusion, the topmost InP layer becomes an n-type 1nP multiplication layer 3.
6 (undoped, 0.6 μm) and p-type InP layer 37 (
A pn junction 38 was formed by Zn diffusion (2 μm).

After forming a protective film 39 on the side surface of the mesa, oxygen was introduced by ion implantation to form a semi-insulating region 40. 700
℃ for 1 minute, the p electrode 41. An n-electrode 42 was formed to form an APD. When we measured the characteristics of this device, we found that the reverse breakdown voltage VB was approximately 80V, the dark current at a reverse bias voltage of 10V was less than 1nA, the dark current at 0.9Va was approximately 20nA, and the maximum multiplication factor was approximately 40. Ta. In terms of reliability, no deterioration was observed even after 1000 hours in a reverse bias current test at 0.9 Va.

Embodiment 2 This embodiment, which will be explained with reference to FIG. 5, is the same as Embodiment 1 except that the p-electrode 41 is used as a pattern electrode, and the n-electrode 42 is used as a surface-light-incident electrode. In terms of characteristics, almost the same performance as in Example 1 was obtained.

〔Effect of the invention〕

According to the present invention, by making the mesa side surface semi-insulating by introducing inert impurities, it is possible to reduce dark current and improve reliability, which have been problems in conventional mesa-type light receiving elements. Therefore, a light-receiving element with good characteristics can be obtained with good reproducibility, which has great industrial effects.

Although the present invention has been explained using APD as an example, for example, p
It is clear that this effect is commonly exhibited in mesa-type light receiving devices having a pn junction, such as in-photodiodes. Further, regarding the material, although the embodiment has been described using an InP-based material as an example, it is clear that the same effects as in the embodiment can be obtained with, for example, a GaAs-based material, etc., regardless of the material.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of an APD showing the basic concept of the present invention, Fig. 2 is a longitudinal sectional view of a conventional APD, and Fig. 3 is a longitudinal sectional view of a conventional APD.
FIGS. 4 and 5 are vertical cross-sectional views showing an inPD, and FIG. 5 is a vertical cross-sectional view showing an embodiment of the present invention. In order to make the drawings more concise, the hatching is limited to regions that have been made semi-insulating by implanting inert impurities. 1.31-n-type InP substrate, 2,33-n-type InGa
As light absorption layer, 3.35-n-type InP multiplication layer, 4.37
-P-type InP layer, 5.38-pn junction, 6,42...
Semi-insulating region, 7.39...insulating film. 1st birthday

Claims (1)

[Claims] 1. In a semiconductor light receiving device including a mesa type semiconductor light receiving element having a pn junction, a part or all of the region including at least the end of the pn junction on the side surface of the mesa is made into an insulator by introducing an inert impurity. Or a semiconductor light receiving device characterized by being made of a semi-insulating material. 2. A method for manufacturing a semiconductor light receiving device, comprising forming the inert impurity-introduced layer of the semiconductor light receiving device according to claim 1 using ion implantation of protons or oxygen. 3. The method of manufacturing a semiconductor light receiving device according to claim 2, wherein after forming an insulating protection film on the side surface of the mesa, an inert impurity is introduced into the side surface of the mesa through the insulating protection film.