JPS59161082A - Semiconductor light-receptor - Google Patents

Abstract

PURPOSE:To eliminate a sudden change in a composition in the hetero-interface constituted by a buffer layer and an optical absorption layer, and to prevent the deterioration of light-receiving characteristics by interposing an intermediate layer between the optical absorption layer and a multiplication layer on interposing the intermediate layer on the side reverse to the side where the optical absorption layer and the multiplication layer are in contact or between the multiplication layer and a semiconductor substrate. CONSTITUTION:The semiconductor light-receptor differs from conventional devices in a point where an intermediate layer 9 is interposed between a buffer layer 2 and an optical absorption layer 3. The intermediate layer 9 has a composition intermediating between the buffer layer 2 and the optical absorption layer 3. A phenomenon in which a nuclear hetero-interface has photo sensitivity is not generated even when a depletion layer reaches to the hetero-interface because a sudden change in the hetero-interface by the buffer layer 2 and the optical absorption layer 3 is relaxed owing to the presence of the intermediate layer 9.

Description

Detailed Description of the Invention Technical Field of the Invention The present invention relates to a semiconductor heterojunction structure avalanche in which a light absorption section that absorbs light and generates carriers and a multiplication section that multiplies the optically excited carriers are separated. Multiplying photodetector (separ)
ated absorptton multipl
cation-avalanche photo
This invention relates to an improvement of a semiconductor light receiving device called diode (SAM-APD).

PRIOR ART AND PROBLEMS FIG. 1 is a cutaway side view of essential parts showing a conventional example of a SAM-APD.

In the figure, 1 is an n+ type substrate, 2 is an n-type buffer layer, and 3
is an n-type light absorption layer, 4 is an n-type multiplication layer (window layer), and 5 is an n-type light absorption layer.
is p-plastic or p+ type impurity introduced region, 6 is p-side electrode, 7 is
indicates the n-side electrode, respectively. In addition, GaAs-Ga
In the case of AlAs, the substrate 1 is GaAs, the buffer layer 2 is GaAlAs, and the light absorption layer 3 is Qa.
, As, and GaAlAs are used as the multiplication layer 4, and in the case of InP-1nGaAs (P) system,
InP as the substrate 1, InP as the buffer layer 2,
InGaAs (P) is used as the light absorption layer 3, and InP is used as the multiplication layer N4.

In the illustrated example, the p + type impurity doped region 5 is an n type multiplication N
4 by diffusing p-type impurities or implanting p-type impurity ions, and the composition of each layer forming the heteroconvex junction has an energy band gap such that Eg (3)<Eg (4), Eg (2).

Now, in this conventional example, light of a specific wavelength is absorbed by the n-type light absorption layer 3, thereby exciting carriers.

The carriers are accelerated in the high electric field depletion layer extending from the pn junction of the n-type multiplication layer 4 and the p-type impurity-introduced region 5 by the reverse bias voltage applied to the electrodes 6 and 7, and avalanche due to the impact ionization phenomenon. It is something that is multiplied.

FIG. 2 is a cutaway side view of main parts showing another conventional example.

The difference between this conventional example and the conventional example explained with reference to FIG. 1 is that the energy band gap Eg between the light absorption layer 3 and the multiplication layer 4 is This is because a thin intermediate layer 8 which is located in the middle and has sufficient lattice matching with the light absorption layer 3 and the multiplication layer 4 is interposed. The material for the intermediate layer 8 is InP-1nGaAs, which is InGaAsP having a composition that is lattice matched to the InGaAsP light absorption layer 3 and the InP multiplication layer 4 and whose energy hand gap is larger than that of the InP light absorption layer 3. are using.

It has been reported that the provision of such an intermediate layer 8 significantly improves the frequency characteristics of a semiconductor light receiving device. The reason for this is that by interposing the intermediate layer 8, the size of the hetero barrier (energy barrier) in the conventional example shown in FIG. 1 is divided into two, resulting in minority carriers, in this case holes. This is thought to be because it becomes easier for people to cross the barrier.

By the way, in the above-mentioned two conventional examples as well as in other conventional techniques, no consideration is given at all to the problem at the hetero interface constituted by the buffer layer 2 and the light absorption layer 3.

According to the findings of the present inventor, when the reverse bias voltage applied between the electrodes 6 and 7 becomes sufficiently large and the depletion layer reaches the hetero interface composed of the buffer layer 2 and the light absorption layer 3, , it has been found that the light-receiving characteristics are significantly inhibited because the light-sensitivity occurs over a wide region along the hetero-interface.

The reason for this is that, as a result of various experiments, there is a sudden change in the composition at the hetero interface between the buffer layer 2 and the light absorption layer 3, that is,
It has been determined that discontinuity is the problem.

Purpose of the Invention The present invention provides a semiconductor light receiving device that has a heterojunction structure and utilizes sag multiplication, in which a sudden change in composition at a heterointerface consisting of a buffer layer and a light absorption layer is achieved. This is intended to eliminate the change and prevent deterioration of the light receiving characteristics.

Structure of the Invention In the present invention, an intermediate layer similar to the intermediate layer 8 seen in the conventional example explained with reference to FIG. 2 is also formed between the buffer layer and the light absorption layer.

FIG. 3 is a cross-sectional side view of essential parts showing the structure of the semiconductor light receiving device according to the present invention, and the same parts as those explained in connection with FIG. 2 are indicated by the same symbols.

This semiconductor light receiving device differs from the conventional example shown in FIG. 2 in that an intermediate layer 9 is interposed between the buffer layer 2 and the light absorption layer 3.

It goes without saying that this intermediate layer 9 has a composition intermediate between that of the hesophagus layer 2 and the light absorption layer 3.

The presence of this intermediate layer 9 alleviates the sudden change at the hetero interface between the buffer layer 2 and the light absorption layer 3, and therefore prevents the depletion layer from reaching the hetero interface. However, the phenomenon that the hetero-interface becomes photosensitive never occurs.

Embodiment of the Invention Adopting the configuration shown in FIG. 3, InP-IndaAs
When we fabricated a SAM-APD system, we found that the wavelength was 1.6 [μ
m], the multiplication number M-30 (0.9V, B,
VB = 60' (V)), frequency response 1, 6 (
GHz) (-3(dB)).

Its specifications are as follows. Note that the symbols are the same as those shown in the drawings.

Symbol 1 Semiconductor: n+ type 1nP Crystal axis: <111>A Thickness: 100 (μm) Carrier concentration: ' n = I x 1016 (cm-
3) 2 Semiconductor Zn type 1nP Thickness: a, O [μm] Carrier concentration: n = I x 10” (cm-3)
3 Semiconductor: n-type 1 n Ga A's energy
Band gap (wavelength conversion): /1g=1.6C
μ-bu〕 Thickness: 2.0Cμm〕 Carrier concentration: n=5・X 10” [cm-3)
4 Semiconductor: n-type 1nP Thickness: 2.0 (μm) Carrier concentration: n-I x 10''(cm-'')
5 Semiconductor; p+ type 1nP Impurity: Cd Depth: 1 [μm] 6 Material: Au-Zn Thickness: 2000 (people) 7 Material: Au-Ge-Ni Thickness [000 (people)] 8 Semiconductor Zn type 1 nGaAs p Energy band gap (wavelength conversion): λg=1.
3cμm] Thickness: 0.3Cμm] Carrier concentration: n = 5 x 101S (cm =)
9 Semiconductor: n-type 1nGaAsP Energy band gap (wavelength conversion): λg=1,
3 (μm) Thickness:, 0.3Cμm] Carrier concentration: n = I
-3) Effects of the invention In the semiconductor light receiving device of the present invention, an intermediate layer having a composition intermediate between the light absorption layer and the multiplication layer is interposed between the light absorption layer and the multiplication layer, and Between the light absorption layer and the semiconductor layer or semiconductor substrate that is in contact with the side of the light absorption layer that is in contact with the multiplication layer and the opposite side; Since there is an intermediate layer having a composition of When the layer reaches the layer, the phenomenon that occurs on the surface with photosensitivity can be completely eliminated, so deterioration of the light-receiving characteristics can be prevented.

[Brief explanation of the drawing]

1 and 2 are cross-sectional side views of essential parts of a semiconductor light-receiving device for explaining a conventional example, and FIG. 3 is a cross-sectional side view of main parts of a semiconductor light-receiving device for explaining the present invention. In the figure, 1 is an n+ type substrate, 2 is an n-type haphazard layer, and 3
is an n-type light absorption layer, 4 is an n-type multiplication layer (window layer), and 5 is an n-type light absorption layer.
is a p-formic acid or p+ type impurity-introduced region, 6 is a p-side electrode, 7
is an n-side electrode, and 8 and 9 are intermediate layers.

Claims (1)

[Claims] In the avalanche multiplication type semiconductor light receiving device having a semiconductor heterojunction structure in which a light absorption layer that absorbs light and generates carriers and a multiplication layer that multiplies the light-excited carriers are separated, an intermediate layer formed between the light absorption layer and the multiplication layer and having a composition intermediate between that of the light absorption layer and the multiplication layer;
A semiconductor layer formed between the side of the light absorption layer that is in contact with the multiplication layer and a semiconductor layer (or semiconductor substrate) that is in contact with the opposite side, and that is in contact with the light absorption layer and the opposite side. (or a semiconductor substrate).