JPH0251284A - Semiconductor light receiving element - Google Patents

Abstract

PURPOSE:To make it possible to sharply reduce noise resulting from surface leakage currents of a semiconductor base substance by placing the third electrode on the way of a surface leakage path between the first and second electrodes in a semiconductor base substance so as to apply potential. CONSTITUTION:The first electrode 9 is connected to a substrate 1 at the bottom of a semiconductor base substance 7, and the second electrode 10 is connected to a light receiving region (diffusion layer) 5 at the top of the semiconductor base substance 7, while the third electrode 11 presents annulation and is so connected as to surround a light receiving region 5 to the outside region of the light receiving region 5 at the top of the semiconductor base substance 7. And the power source potential of the first electrode 9, that is, the positive side of the power source E is directly applied to the third electrode 11.

Description

[Detailed Description of the Invention] [Summary] Regarding a semiconductor light-receiving element that applies a voltage for photodetection between electrodes provided on the upper and lower surfaces of a semiconductor substrate, noise contained in a detection signal, particularly caused by surface leakage current of the semiconductor substrate. For the purpose of reducing the noise generated by a second electrode connected to the light receiving area;
a third electrode surrounding the light-receiving region in a closed or partially open annular shape on the upper surface and connecting to an outer region of the light-receiving region;
A photodetection voltage is applied between the first and second electrodes, and the third
The electrodes are configured so that the power supply potential of the first electrode is applied, and the first electrode becomes the output end of the detection No. 13.

[Industrial application field]

The present invention relates to a semiconductor light receiving element that applies a voltage for photodetection between electrodes provided on the upper and lower surfaces of a semiconductor substrate.

The semiconductor light-receiving elements include APDs (avalanche photodiodes) and pin-p() (pin type photodiodes), which are compatible with applications requiring high speed such as optical communication.

When a semiconductor such as GaSb is used as a semiconductor substrate to improve high-speed performance, it is difficult to improve crystallinity or stabilize the surface condition, which may increase surface leakage. It is desirable to prevent noise from being mixed into the detection signal.

[Conventional technology]

FIG. 4 is a schematic side sectional view of a conventional example of an APD with improved high-speed performance.

In the figure, 1 is an n''-GaSb substrate, 2 is an n--G
asb absorption layer, 3 is n--Alx Gap-xSb (
x = 0.065) Multiplier layer, 4 to n-1 IxGap-
xSb (x = 0.3) window layer, 5 a p+-diffusion layer serving as a light-receiving region, and 6 a guard ring consisting of a ρ--diffusion layer, which constitute a semiconductor substrate 7.

Further, 8 is a SiN passivation film, 9 is a first electrode connected to the substrate I, and 10 is a ring-shaped second electrode connected to the diffusion layer 5 serving as a light receiving area.

This element detects light by applying a positive side to the electrode 9 and a negative side to the electrode 10 from the power source E, and the electrode 9 or 10 serves as the output end of the detection signal.

In this conventional example, an AlGaSb material is used as the material of the semiconductor substrate 7, in order to increase the ionization rate ratio, thereby speeding up the device operation, and at the same time, hoping to reduce noise. By the way, the conventional normal APD is InG
When using the aAs system, the ionization rate ratio is about 2.5, but
The ionization rate ratio in this conventional example is expected to be 10 or more.

[Problem to be solved by the invention]

However, in the conventional example described above, the surface leakage current (A in the figure) due to the surface inversion layer is much larger than that in the case where 1nGaAs system is used in the semiconductor substrate 7 due to the characteristics of the material (^1Gasb system). Since the current passes through the output end, large shot noise generated by surface leakage current is included in the output signal, which poses a practical problem.

SUMMARY OF THE INVENTION Therefore, the present invention aims to reduce noise contained in a detection signal, particularly noise caused by surface leakage current of a semiconductor substrate, in a semiconductor light receiving element that applies a voltage for photodetection between electrodes provided on the upper and lower surfaces of a semiconductor substrate. With the goal.

[Means to solve the problem]

FIG. 1 is a schematic side sectional view of the embodiment.

[1] As shown in FIG. an electrode 9 and a second electrode 1 connected to the light receiving area 5 on the upper surface of the base 7
0, and a third electrode 1 surrounding the light receiving area 5 in a closed or partially extenuating annular shape on the upper surface and connecting to the outer area of the light receiving area 5.
1, a voltage for photodetection is applied between the first and second electrodes 9 and 10, a power supply potential of the first electrode 9 is applied to the third electrode 11, and the first electrode 9 receives a detection signal. This problem is solved by the semiconductor light-receiving element of the present invention, which serves as an output terminal.

[For production]

The third electrode 11 is connected to the first and second electrodes on the conductor base 7.
The above-mentioned potential is applied in the middle of the surface leak bath between electrodes 9 and 10. Therefore, the conventional first and second electrodes 9.1
The large surface leakage current that had been flowing between the two electrodes 10 and 11 is narrowed between the second and third electrodes 10 and 11, and the surface leakage current that passes through the first electrode 9, which is the output end, becomes minute.

As a result, noise contained in the detection signal, particularly noise caused by surface leakage current of the semiconductor substrate 7, is significantly reduced.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. As mentioned above, FIG. 1 is a schematic side sectional view of the embodiment;
FIG. 2 (al) is a side sectional view showing the manufacturing process of the embodiment, and FIG. 3 is a schematic side sectional view of another embodiment, and the same reference numerals indicate the same objects throughout the drawings.

In FIG. 1, the embodiment shown in the figure is an APD in which a third electrode 11 is added to the conventional example shown in FIG. 4, and the output end is limited to the first electrode 9.

That is, the first electrode 9 is connected to the substrate 1 on the lower surface of the semiconductor substrate 7, and the second electrode IO is connected to the light receiving region (diffusion layer) 5 on the upper surface of the semiconductor substrate 7, whereas the third electrode 11 has an annular shape and is connected to the outer region of the light receiving region 5 on the upper surface of the semiconductor substrate 7, surrounding the light receiving region 5. And the third electrode 11
is applied directly to the power supply potential of the first electrode 9, that is, the positive side of the power supply E.

From this, it can be seen that the large surface leakage current that spread between the first and second electrodes 9 and 10 in the conventional example is reduced between the second and third electrodes 101 and 10.
11, the surface leakage current passing through the first electrode 9, which is the output end, becomes minute, and the noise contained in the detection (No. 3), especially the noise caused by the surface leakage current of the semiconductor substrate 7, is significantly reduced. do.

This element can be manufactured roughly as follows.

First of all, referring to FIG. --AlxGa, -xSb (x = 0.3
) The wind layer 4 is sequentially grown at a growth temperature of 615°C.
grow up. The compositions of the melts and their ratios are as follows.

Ga: Sb: Tc = 0.155: 0.845: 5 Xl0-
'Al: Ga: Sb: Te = 1.5X10: 0.148: 0.850
5: 5 x 10-'re -3xlO-': 0.129: 0.868
: 5 xlO-' then FIG. 2 (see bl.
After diffusing or ion-implanting Cd to form a p+ light-receiving region 5, which is a diffusion layer, and a p- guard ring 6, a SiN passivation film 8 is deposited on two surfaces, and second and third electrodes 9. Open the contact window for 10.

After this, a first electrode 9 is formed on the lower surface, and a second electrode 10 and a third electrode 11 are formed on the second surface, thereby completing the APD element shown in FIG.

Through the above steps, the substrate 1, the absorption layer 2, the multiplication 11x3,
The thickness of the wind layer 4 is 350 μm and 1.5 μI, respectively.
11.21) m, 2 μm, and the outer diameter of the light receiving area 5 is 10
0 μmφ, the outer diameter of the guard ring 6 is 13011pφ, the size of the semiconductor substrate 7 is 300 μm square, and the diameter of the connection part with the window layer 4 is 200 μmφ.
When the dark current at the output end, which is an index of the noise contained in the detection signal, was compared, the dark current in the example was about 115 compared to the conventional example.

Here, the third electric wedge 11 is formed into a closed ring shape, but the ring may be partially open. However, in that case, it is necessary to take into consideration that the surface leakage current to the first electrode 9 increases depending on the size of the opening.

Although the embodiment described above is of a planar type, the present invention can also be applied to a mesa-embedded type, for example, as shown in FIG. 3 showing another embodiment.

In FIG. 3, 21 is an n''-Gash substrate, 22 is an n
--(J a S b absorption layer, 23 is n--81xGa
, -xSb (x = 0.065) multiplication layer, 24 is p''
AIX Ga1-xSb (x = 0.3) Wind layer, Wind layer 24, Multiplier layer 23, Absorption layer 2
2 forms a mesa, and the upper layer of the mesa becomes a light receiving area 25.

Also, 26 is IxGa, x to n-1 filling the outside of the mesa.
This is an Sb (x=0.3) embedded layer, and the semiconductor body 27 is made of the above semiconductor. Further, 28 is a SiN association II, 29 is a first electrode connected to the substrate 21, 30 is a second electrode connected to the light receiving area 25, and 31 is a 3' electrode connected to the buried layer.

The following examples are for API), but the present invention
It goes without saying that the present invention can also be applied to other light receiving elements such as pin-PDs. And semiconductor No. 1 (very effective when the body has a large surface leakage).

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, in a semiconductor light receiving element that applies a voltage for photodetection between electrodes provided on the upper and lower surfaces of a semiconductor substrate, noise contained in a detection signal, particularly surface leakage current of the semiconductor substrate, can be detected. It is possible to reduce the noise caused by 1! (2) It has the effect of making it possible to significantly reduce noise when the l''4-body substrate has a large surface leakage.

[Brief explanation of the drawing]

Fig. 1 is a schematic side sectional view of the embodiment, Fig. 2 f8+ (b) is a side sectional view showing the manufacturing process of the embodiment, Fig. 3 is a schematic side sectional view of another embodiment, and Fig. 4 is the conventional This is a schematic side sectional view of an example. In the figure, 1.2] is a ridge-GaSb substrate (semiconductor substrate) 5 is p+-
25 is a light receiving area; 7.27 is a semiconductor substrate; 9.29 is a first electrode; 10.30 is a second electrode; 11.31 is a third electrode. Meiyan@ no drifting face 10 寥 1 ro

Claims (1)

[Claims] A semiconductor substrate (7) having a light-receiving region (5) of a conductivity type opposite to that of the main body on the upper surface side, a first electrode (9) connected to the substrate (7) on the lower surface of the substrate (7); a second electrode (10) connected to the light receiving area (5) on the upper surface of the base (7);
a third electrode (11) surrounding the light-receiving region (5) in a closed or partially open annular shape on the upper surface and connecting to an outer region of the light-receiving region (5); , 10) have a photodetection voltage applied between them, and the third electrode (11)
A semiconductor light-receiving element characterized in that a power supply potential of an electrode (9) is applied, and the first electrode (9) serves as an output end for a detection signal.