JPH01169976A - Semiconductor photo-detector - Google Patents

Abstract

PURPOSE:To improve quantum efficiency, and to inhibit the tunnel currents of a junction by covering a light-receiving region with AlxGa1-xSb(0<x<1) having a large band gap so as to completely transmit 1.55mum-light and forming a p-type region and a guard ring to AlxGa1-xSb. CONSTITUTION:An n-type GaSb optical absorption layer 2, an n-type AlxGa1-xSb(0<x<1) multiplication layer 3, an n-type AlxGa1-xSb(0<x<1) window layer 4, and a p-type region 5 are shaped successively from on top of a substrate, including a light-receiving region. The ionization rate of the multiplication layer 3 displays a peak value. The window layer 4 has an impurity concentration lower than that of the multiplication layer 3 and a band gap larger than that of the multiplication layer 3. The region 5 is composed of AlxGa1-xSb(0<x<1) having a band gap larger than the multiplication layer 3. The window layer 4 constitutes a guard ring in contact with the side face of the region 5 and the side face of the multiplication layer 3. Accordingly, quantum efficiency is improved, and the tunnel currents of a junction are inhibited.

Description

[Detailed description of the invention] 〔overview〕 Regarding the structure of AlGaSb-based APD.

In addition to providing a strong guard ring effect.

The aim is to obtain a structure that can increase quantum efficiency through the wind effect.

N-type GaSb layered in order including the light-receiving region on the substrate
with a light absorption layer.

1. To an n-type composition with a side surface exposed at the light-receiving region interface and a peak ionization rate ratio. Gal-xSb (0<x<1) multiplication layer.

An n-type A1. Gal-xSb (0<x<1) wind layer.

The window layer has a p-type region made of ^lXGa I-xsb (0<x<1) with a larger reband gap than the multiplication layer, and the window layer extends from the light-receiving region to the side surface of the p-type region and the multiplication layer. A guard ring is formed in contact with the side surface of the double layer.

[Industrial application field]

The present invention relates to AlGaSb-based APD (Avalanche
Regarding the structure of Phtodiode).

With the increasing distance and capacity of optical communication systems.

The AlGaSb-based APD is A1. Ga, -, Sb is x
Utilizing property 1) that the ionization rate ratio increases resonantly and shows a peak value at =0.065, 1. It is expected to be used as an ultra-low-noise, ultra-high-speed photodetector.

1) 0. Hildebrand et al.

IEEE Journal of Quantun+
Electronics, 'VOL, Qt! -17,
No, 2. p, 284-288°February
1981゜[Prior art] Generally, in APD, pn is efficiently transmitted in the light receiving area.
In order to cause junction breakdown and multiply carriers, a strong guard ring is required to increase the withstand voltage of the pn junction around the light receiving region.

There are very few examples of realizing planar APDs using AlGaSb (and there is also little information regarding guard ring breakdown voltage).

FIG. 3 is a cross-sectional view of a conventional AlGaSb-based APD.

In the figure, n-G
aSb light absorption layer 2, n-A1. Ga1−xSb(x
=0.065) Multiplier layer 3゜n-Al, Ga1-X5b (
x=0.3) Grow the wind layer 4A.

Zn is diffused in the window layer 4A leaving a part of the thickness.

A highly doped p-type region 5 is formed.

6 is a ring-shaped p-side electrode, and 7 is a substrate-side n-side electrode.

In this example, all the layers can be formed in one epitaxial growth, but the electric field tends to concentrate at the peripheral edge of the p-type region 5, so the junction is likely to break down here, and the light-receiving region is not sufficiently increased. There is a drawback that you cannot get double the amount.

Therefore, FIG. 4 shows a structure in which a guard ring is added to prevent breakdown at the periphery of the bond.

FIG. 4 is a sectional view of another conventional AlGaSb APD.

In the figure, n-G
aSb light absorption layer 2. n-^lXGa+-xSb (x=0
．． 065) Multiplier layer 3 is grown and etched into a mesa shape leaving a light receiving area.

Next, leaving the etching mask for forming the mesa as it is, the area around the mesa is etched with a low concentration of n--A1. Buried growth with Ga+-xsb (x=0.3).

A guard ring 4B is formed.

Next, Zn is diffused from the surface into the multiplication layer 3 in the light receiving region and a part of the guard ring 4B adjacent thereto.

A highly doped p-type region 5 is formed.

6 is a ring-shaped p-side electrode, and 7 is a substrate-side n-side electrode.

In this example, the junction peripheral edge is formed within the low concentration n-^1XGa+-xSb (x=0.3) guard ring 4B, and the A1. Ga,
□5b (x=0.3) is the multiplier layer 81xGa + -X
The ionization rate is lower than that of Sb (x = 0, 065), and the breakdown voltage is higher.

Due to the guard ring effect based on this reason, breakdown around the bond can be prevented.

[Problem that the invention seeks to solve]

However, A1. shown in FIG. Ga+-, Sb
According to the spectral sensitivity characteristics, even when light with a wavelength of 1.55 μm is incident from the element surface, the multiplication layer has sensitivity, although it is small. Therefore, the light is absorbed in the p-type region 5 and the multiplication layer 3. This causes the inconvenience of

In such a state, the effect of mixed injection of electrons and holes into the multiplication layer becomes large, making full use of the characteristics of AlXGa1-xSb (x = 0.065), which has a high ionization rate ratio due to resonance ionization reduction. I can't do it.

Noise increases.

In addition, the light absorbed by the p-type region 5 contributes as a photocurrent only to the electrons 3 or holes that have diffused into the depletion layer generated by applying a reverse bias to the junction, thereby reducing the quantum efficiency.

[Means for solving problems]

The solution to the above problem is to use an n-type GaSb light absorbing layer that includes a light receiving region and is laminated in order on a substrate.

N-type A with a composition in which the side surface is exposed at the interface of the light-receiving region and the ionization rate ratio exhibits a peak value 1. Ga I −xsb (0< x 〈1)
With multiplication layer.

an n-type l Ja + -xSb (0<x<1) wind layer having a lower impurity concentration than the multiplication layer and a larger band gap than the multiplication layer;

A1. has a larger reband gap than the multiplication layer. a p-type region consisting of Ga+-xSb (0<x<1), and the window layer extends from the light-receiving region to form the p-type region.
This is achieved by a semiconductor light receiving element forming a guard ring in contact with the side surface of the mold region and the side surface of the multiplication layer.

[Effect]

The present invention is an AlGaSb-based AP with a guard ring effect.
This gives D a wind effect. That is, as shown in FIG. 2, Al
Cover the light receiving area with Ga, , , XSb (X = 0.3).

A p-type region and a guard ring are formed here.

As a result, light of 1.55 μm can reach the depletion layer without being absorbed by the p-type region 5.

〔Example〕

FIG. 1 shows an AlGaSb-based APD according to an embodiment of the present invention.
FIG.

Next, the structure will be explained in order of the manufacturing process.

In the figure, n-G
aSb light absorption layer 2. n-81XGa + -, Sb (
x = 0.065) The multiplication layer 3 is grown and etched into a mesa shape, leaving a light receiving area.

Next, the etching mask for mesa formation was removed.

Low concentrations of n-A1 cover the mesa. Ga+−xSb(x=
0.3) Grow the wind layer 4.

This layer becomes a guard ring in the buried portion.

Next, Zn is diffused into the window layer 4 from the surface to form a highly concentrated p-type region 5 in a region including the light-receiving region.

The specifications of each part mentioned above are as follows.

Drawing number Each part F-Vanthope concentration Thickness (c
m-3) (μm) 5 p””-8 to Gasb Zn
IE19 14 n--AlG
aSb Te 2E15 2/1.23
n--AlGaSbTe 5E15
110.22 n-GaSbTe5
E15 11 n”-GaSb
Te IE18 3506 is a ring-shaped p
side electrode, thickness 360/60/100 Au/Zn/
An Au/Ti layer with a thickness of 2700/300 is formed on the Au layer, and 7 is the n-side electrode on the substrate side with a thickness of 2700/3.
00 All/AllGe layers.

In the embodiment, the junction was formed in the window layer, but even if the junction is formed a little into the multiplication layer, the quantum efficiency will only decrease to some extent and there will be no major problem.

Also, A1. In Ga+-, Sb-based crystals, increasing X only slightly increases the lattice constant, but in order to further improve lattice matching, 1 As is added to this crystal system to control lattice matching as a quaternary crystal. You may go.

〔Effect of the invention〕

As explained above, according to the present invention, a strong guard ring effect can be obtained in an AlGaSb-based APD, and quantum efficiency can be increased due to the wind effect.

Furthermore, since the junction is formed in the wind layer/guard ring with a large band gap, tunnel current in the junction that does not contribute to multiplication can be suppressed.

[Brief explanation of the drawing]

FIG. 1 shows an AlGaSb-based APD according to an embodiment of the present invention.
Cross-sectional view. FIG. 2 is a spectral sensitivity characteristic diagram of Haru AlXGa+-xSb. FIG. 3 is a cross-sectional view of a conventional AlGaSb-based APD. FIG. 4 is a sectional view of another conventional AlGaSb APD. In fig. 1 is an n"-GaSb substrate. 2 is an n-GaSb light absorption layer. 3 is an n-AtXGa+-xSb (x=0.065) multiplication layer. 4 is an n-AlxGa+-xsb (x=0.3) window 5 is the p-type region. 6 is the p-side electrode, Au/Ti layer/Au/Zn/Au layer. 7 is the n-side electrode Au/AuGe layer Aixl: rαI-x S)) / 72 /, 4 1 .6 /, 8
2.0 temporary length. Showari Tokuwatoku・Fukuro 2 Figure 3 Figure tf) fli I9・jq I! 117 f5 Fig. 4

Claims (1)

[Scope of Claims] An n-type GaSb light absorption layer laminated in order including a light-receiving region on a substrate, and an n-type Al_xGa_1_-_xSb whose side surface is exposed at the interface of the light-receiving region and whose ionization rate ratio exhibits a peak value. (0<x<1) multiplication layer, an n-type Al_xGa_1_-_xSb (0<x<1) window layer which has a lower impurity concentration than the multiplication layer and has a larger reband gap than the multiplication layer; A p layer made of AlxGa_1_-_xSb (0<x<1) with a larger band gap than the multiplication layer
type region, and the window layer extends from the light-receiving region and forms a guard ring in contact with a side surface of the p-type region and a side surface of the multiplication layer.