JPS58158978A - Semiconductor photodetector - Google Patents

Abstract

PURPOSE:To eliminate a special guard ring structure in a photodetector having one conductive type InGaAs layer to become a photoabsorbing layer and one conductive type InP layer to become avalanche amplification layer by sequentially forming one conductive type layer on a high resistance InP substrate having a region including reverse conductive type impurity. CONSTITUTION:A P type region 12 including P type impurity is diffuse in a semi-insulating InP substrate 10, and N type InP layer 11 and an N type InGaAs layer 12 are sequentially grown o the overall surface including the region 13. P type impurity in the substrate 10 is selectively diffused in the layer 11 by the high temperature during the growth or the heat treatment after the growth at this time, and a P-N junction 14 is produced in the layer 11. Thereafter, the back surface of the substrate 10 is polished until the region 13 is exposed, and a reflection preventive film such as SiO2 or Si3N4 is covered on the substrate. In this manner, the difference between the avalanche breakdown voltage V1 in the substrate 10 and the avalanche breakdown voltage V2 in the layer 11 becomes very large as V1>>V2, and the breakdown can be prevented at the end of the junction even if no guard ring is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a semiconductor light receiving element having an avalanche multiplication effect.

Prior Art and Problems As a light-receiving element material that operates in the wavelength band (1 to 1.6 μm) where optical fibers exhibit low loss, a ternary compound semiconductor 1rLo, 55 Gaa, 4y A' lattice-matched to InP is used.
(hereinafter abbreviated as 1nGaAz) is known. JnGa
In order to realize a high-performance light-receiving element with low dark current and high quantum efficiency using AI, I%QmAz is combined with InP, avalanche multiplication is performed within the 1%2 layer, and light absorption is reduced by InG.
A structure has been proposed in which this is done within the aAz layer.

FIGS. 1A to 1C are cross-sectional views showing different conventional examples of this type of light receiving element.

In the same figure (A), n-type 1xP
Grow layer 2, cylindrical 1*GaAz layer 3, after which P+
Appropriate electrodes (not shown) are formed on the IsP substrate 1 and the 1x GaAp layer 3, respectively, and further etched into a mesa shape to prevent breakdown at the junction end. It is an Aparan photodiode with This device structure can be fabricated using well-known epitaxial growth methods, such as vapor phase epitaxy (VPE) and liquid phase epitaxy (VPE).
LPE). However, the same figure (A)
The mesa-shaped photodetector shown in the figure has an exposed junction, so
CB> in the same figure is a light receiving element called a planar type that has improved the above-mentioned drawback, and on the C-type 1vhP substrate 4, the cylindrical I-shaped GtxAa @ 5, the Le-shaped I-P grow layer 6;
Thereafter, a P-type 1nP region 7v is formed by selective diffusion, and a guard ring 8 is further formed to prevent breakdown at the rear end. This structure is usually produced by vapor phase growth. The reason for this is that in the liquid phase growth method, when growing 6v of cylindrical InP layers on the square I% GaAs layer 5, there is a phenomenon in which the InP growth solution dissolves the square I% GaAz layer. .

When manufacturing a planar light receiving element as shown in the same figure (B) by the liquid phase growth method, as shown in the same figure (C), an InGaAzP quaternary WIJ9 k is formed on the tortoise-shaped 1nGaAz layer 5.
Lt, formed during the growth of s-type I%P layer 6
This is to prevent the layer from dissolving. In addition, the same figure (
In C), the same reference numerals as those in the other figure (B) represent the same parts. Furthermore, two or more InGaAsP quaternary layers may be provided.

By the way, in the light-receiving elements shown in CB) and (C) of the same figure, a guard ring 8 is provided to prevent breakdown at the joint end, but manufacturing the guard ring 8 is difficult. There were drawbacks. That is, 3 shapes 1' with joints
Under the nP layer 6, there is a porcelain InGaAz layer 6 or 1*GaAzP.
Since there is a quaternary layer 9, in order to suppress the spread of the depletion layer and effectively exhibit the guard ring effect, the depth of the guard ring 8 should be made almost equal to the depth of the P 10-type 1nP region 7. The drawback was that it required advanced technology. In addition, in the light receiving element shown in CC) of the same figure, IwbGaAzP
In order to grow the square I%P layer 6 without melting the layer 9, a very sophisticated technique was required.

As described above, the conventional light-receiving element having an avalanche multiplication effect has the disadvantage of not only crystal growth but also the necessity of providing a guard ring structure that requires precise manufacturing control.

purpose of invention The present invention improves the above-mentioned drawbacks.

Its purpose is to eliminate the need for a special guard ring structure.

Another object of the present invention is to provide a semiconductor photodetector having a high-performance avalanche multiplication effect. Examples will be described in detail below.

Embodiment 182 of the invention is a cross-sectional view of an embodiment of the invention, where 1° is a semi-insulating InP substrate (hereinafter referred to as semi-insulating 1nP substrate).
, 11 is a le-shaped 1nP layer serving as an avalanche multiplication layer, 12 is an arithmetic circuit GαAs layer serving as a light absorption layer, and 13 is a P shadow region containing a large amount of P-type impurities. Also,'! g3 diagram (,4)
, (B) is a sectional view for explaining an example of a method of manufacturing the light receiving element shown in FIG. 2, and the same reference numerals as in FIG. 2 represent the same parts.

When manufacturing the light receiving element shown in FIG. 2, first, as shown in FIG. 5(A), a P shadow region 15 containing a large amount of P type impurities is selectively formed on a semi-insulating InP substrate 10. . The P shadow region is formed on a semi-insulating 1xP substrate 1D by a method such as a 0-order 5 vapor phase growth method or a liquid phase growth method to which an impurity diffusion method, an ion implantation method, etc. can be applied.
P layer 11. Finger-shaped InGaAz layers 12 are grown one after another.

Due to the high temperature during the growth of the hbP layer 11 and the nGaAz#A12 or the heat treatment after growth, the p-type impurities in the semi-insulating IrLP substrate 10 are selectively diffused into the n-type ITLP layer 11, as shown in the figure ( As shown in B), π-type 1nP J slope 1
A p-x junction 14 is formed in 1. Next, P shadow area 13
The semi-insulating 1nP substrate 10 is thinned until the second
Obtain the structure shown in the figure.

According to this embodiment, crystal growth may be performed by either a vapor phase growth method or a liquid phase growth method, and even when using the liquid phase growth method, there is no need to provide a special quaternary layer as in the conventional example. In addition, the avalanche breakdown voltage V1 and the tortoise shape I in the semi-insulating 1nP substrate 10
Since the difference between the avalanche breakdown voltage Vi within the %P layer 11 is very large (VI>V), breakdown at the junction end can be prevented without providing a special guard ring structure. Therefore,
An electrode (for example, a ring-shaped electrode) that covers a part of the P shadow region 13 and exposes a part is placed on the semi-insulating P substrate 10.
, and in the exposed part of the P shadow area 13, sho,
.

The reason why an anti-reflection film made of Si, N, etc. is formed and an electrode structure is provided in which a portion of the tortoise-shaped region 15 is exposed is to allow light to enter from the exposed portion. In addition, tortoise-shaped 1nGa
It is easily possible using conventional techniques to grow relatively thick quaternary layers, ItsP layers, polycondensed AV recon layers, base-■ group compound semiconductor layers, etc. on As II 12, thereby increasing the strength against Queue. It is. In addition, a high-resistance I%P substrate whose specific resistance is higher than that of the n-type InP layer 11 is used as a semi-insulating substrate.
It is also possible to use it instead of the nF substrate 10.

FIG. 4 is a cross-sectional view of another embodiment of the present invention, in which 15 is a semi-insulating 1nP substrate, 16 is a 3-type rn which becomes an avalanche multiplication layer.
p layer, 17 is an I% GaAp layer which becomes a light absorption layer, 18
is a JmGaAzP quaternary layer containing P-type impurities, 19 is a P shadow region, and 20 is a concave portion. Also, Fig. 5 (A), (B)
4 is a sectional view for explaining an example of a method of manufacturing the light receiving element shown in FIG. 4, and the same reference numerals as in FIG. 4 represent the same parts.

To manufacture the light receiving element shown in Fig. 4, first the photodetector shown in Fig. 5 (
A semi-insulating 1nF substrate 15 as shown in A).

The recess 21 is formed by etching.
), an IGaAzP quaternary layer 18 containing P-type impurities is grown in the recess 21 of the semi-insulating 1nP substrate 15, and further a 11% P layer 16 and an InGaAa layer 1 are formed.
7 to grow sequentially. Shaped I%P layer 16 and Le shaped 1nG
Due to the high temperature during growth of the aAsr layer 17 or the heat treatment after growth, the P-type impurity contained in the InGaAzP quaternary layer 18 is diffused into the 1% type 1rbP layer 16 in the same manner as described above.

The back surface of the zero-order semi-insulating 1rbP substrate 15 on which the P shadow region 19 is formed is etched to form a recess 20 as shown in FIG. In this case, by using an appropriate etching solution (for example, chromium methanol, dichromic acid, etc.), InP and InGaApp can be selectively etched.
It can be automatically stopped at the surface of the FP quaternary layer 18. Note that although the electrodes and antireflection coatings are not shown in the drawings, the electrodes are provided on the square-shaped 1nGaAp layer 17, and
I%GαAsP quaternary around the nGαAIP quaternary layer 1B)
-It is provided so that one part is covered and the other part is exposed. In addition, the anti-reflection film is IrkGttAzp.
It is provided in the exposed part of the quaternary pigeon 18.

! FIG. 186 is a sectional view of another embodiment of the present invention,
22 is a semi-insulating 1nP substrate, 23 is an avalanche multiplication layer
The tortoise-shaped I-circuit PH1, 24 is a 1-nGαA3 layer with light absorption of 1-, and 25 is an InGaA layer containing P-type impurities.
zP 14.26 is a P-type I%P layer, and 27 is a recess.

7(A) to (D>) are sectional views for explaining an example of a method of manufacturing the light receiving element shown in FIG. 6, and the same reference numerals as in FIG. 6 represent the same parts.

To manufacture the light receiving element shown in FIG. 6, first, as shown in FIG. 7(A), a recess 28 is formed in the semi-insulating I%P substrate 22 by etching. Next, as shown in FIG.
A GaAzP quaternary layer 25 and a P-type 1nP layer 26 are sequentially grown. I% GaAzP quaternary layer 25 and p-type I-GaAzP layer 26 are grown at high temperatures during growth or by post-growth heat treatment.
The p-type impurity contained in the P quaternary layer 25 is semi-insulating In
It is diffused into the P substrate 22. Next, selective etching is performed to form convex portions in the grown layer, as shown in FIG. Next, as shown in FIG. CD), the shaped InP layer 2
3. A square-shaped 1nGaAt layer 24 is sequentially grown on the semi-insulating 1nP substrate 22. After this, semi-insulating ll5P substrate 2
The back side of 2 is etched using a selective etching solution to form four parts 27 as shown in FIG.

In this case as well, by using a suitable etching solution (e.g. chromium methanol), etching can be prevented from I-containing GtA.
It can be automatically stopped at the surface of the zP quaternary layer 25. Incidentally, the electrode is provided on the square-shaped GaAz layer 24 and around the InGaAzP quaternary layer 25.

It is provided so as to cover a part of the InGgP quaternary layer 25. In addition, the antireflection film is an InGaAzP quaternary layer 2.
It is provided in the exposed part of No.5.

The photodetector shown in Figures 4 and 6 consists of a P-type 1tsGaAzP quaternary layer 18.25 on a semi-insulating 1nF substrate 15.22
Since the structure is such that the recesses 20 and 27 are embedded in the semi-insulating IsP substrates 15 and 22 during the element manufacturing process,
A selective etching solution can be used to form a Pff! /InGaAzP quaternary @
It has the advantage of being able to automatically stop at the surface of 1B and 25. Further, since the semi-insulating 1nP substrates 15 and 22 play a role as a guard ring, there is an advantage that there is no need to provide a special guard ring structure.

In the example, a round-shaped avalanche multiplication layer and a light absorption layer were provided on a semi-insulating 1nP substrate having a region containing p-type impurities; Of course, a P-type avalanche multiplication layer and a light absorption layer may be provided on a semi-insulating IMF substrate having a region.

Effects of the Invention As explained above, the present invention provides an IrLP layer of opposite conductivity type to serve as an avalanche multiplication layer and an IrLP layer of opposite conductivity type to serve as a light absorption layer on a high-resistance IMF substrate having a region containing impurities of conductivity type. InGalLx layers are sequentially formed, and high resistance I
Since the nP substrate plays the role of a guard ring, there is no need to provide a special guard ring structure, and therefore, there is an advantage that a semiconductor light-receiving element having good characteristics and an avalanche multiplication effect can be easily manufactured. In addition, the necessity of the JnGaAzP quaternary layer 9, which has been a problem in the liquid phase growth method, and the I*GaA
Since there is no deterioration in the quality of the butterfly-shaped 1nP layer 6 due to melting of the zP quaternary layer 9, a high-quality entangled layer I that becomes an avalanche multiplication layer is eliminated.
The MP layer can be easily manufactured, which also has the advantage of making it possible to easily manufacture a high-performance light receiving element. Further, by using InGaAzP as the P shadow region selectively formed on the substrate, there is an advantage that etching can be automatically stopped when forming a recess on the back surface of the substrate.

[Brief explanation of drawings]

Figures 1 (A) to (C') are sectional views of different conventional examples, Figure 2 is a sectional view of an embodiment of the present invention, and Figure 3 (A).
, (B) is a sectional view for explaining the manufacturing method of the element shown in FIG. 2, FIG. 4 is a sectional view of another embodiment of the present invention,
5(A) and CB> are cross-sectional views for explaining the manufacturing method of the element shown in FIG. 4, FIG. 6 is a cross-sectional view of other embodiments of the present invention, and FIGS. 7(A)- (D) is a diagram for explaining a method of manufacturing the element shown in FIG. 6. 1 is a P-type I%P substrate, 2, 6, 11, 16, and 25 are square IMP layers, and 5.5, 12, 17, and 24 are tangled 1nGaA
z layer, 4 is a C-type IMP substrate, 7 is a square 1nF region, 8 is a guard ring, 9, 18.25 is an InGaAzP quaternary layer, 10, 15. 22 is a semi-insulating IP substrate, 15 and 19 are p shadow regions,
14 is a P-staff joint, 20, 21, 27, and 28 are recesses, and 26 is a P-shaped 9IP layer. Patent Applicant: Nippon Telegraph and Telephone Public Corporation Patent Attorney Gobe Tamamushi (3 others) Figure 1 (A) jF! 2 Figure 3 Figure 3 (B)

Claims (1)

[Claims] In a semiconductor photodetector having an InGaAz layer of one conductivity type serving as a light absorption layer and an InP layer of one conductivity type serving as an avalanche multiplication layer, a high resistance 1nP substrate having a region containing impurities of the opposite conductivity type is used. The - conductivity type InP layer and l5G
A semiconductor light-receiving device characterized by sequentially forming aAz layers.