JPH05160428A - Semiconductor light receiving device - Google Patents

Abstract

PURPOSE:To prevent crosstalks from being generated in a semiconductor light receiving device, by making the diffusion length of carriers at the hetero- interface short through very simple means and suppressing the diffusion of the carriers generated due to incident light. CONSTITUTION:In a semiconductor light receiving device, an n-InP buffer layer 2, an n-InGaAs light absorbing layer 3, and an n-InP window layer 4 are formed in succession, and these layers constitute a hetero-junction structure. Also, in the device, provided are n<+>-InGaAs carrier diffusing suppressing layers 11, 12 inserted into the respective hetero-interfaces of the hetero-junction structure, and a plurality of p<+>-window regions spaced in parallel and having depths from the surface of the device to the n-InGaAs light absorbing layer 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a semiconductor light receiving device in which a plurality of light receiving elements are arranged and which is suitable for transmitting an optical signal in parallel.

At present, the field of communication using optical fibers is expanding and diversifying. For example, the wiring of a computer is changed from a conventional coaxial cable to 10 cores to 40 cores.
The so-called parallel transmission is about to be performed, in which computer data is sent in parallel by replacing the core with a ribbon optical fiber.

Therefore, as a matter of course, the light-emitting or light-receiving device used therein is not one in which a single element is built in a conventional one chip, but one in which a plurality of elements are arranged in one chip. There must be. However, such a light emitting device or light receiving device still has many points to be improved.

[0004]

2. Description of the Related Art Generally, when semiconductor light receiving elements are arranged in parallel on the same chip and built in, cross talk between the elements becomes a problem. In particular, InP / InGaAs / InP
As described above, a semiconductor photodetector using a heterostructure in which semiconductor layers having different forbidden band widths are stacked poses a serious problem.

The reason is that the diffusion length of carriers at the hetero interface formed between the semiconductor layers is very long.
Carriers generated due to light incident on a certain element often enter an adjacent element, and this is because the so-called cross talk level is high.

Therefore, various attempts have conventionally been made to suppress such cross talk. FIG. 6 is a cutaway side view of a main part of a conventional example of a semiconductor light receiving device having a structure for preventing cross talk. In the figure, 1 is an n ⁺ -InP substrate, 2 is an n-InP buffer layer, 3 is n
-InGaAs light absorption layer, 4 is an n-InP window layer, 5 is a mesa groove for separating elements, 6 is a p ⁺ -window region, 7 is a non-reflective coating film made of SiN _x , 8 is a p-side electrode , 9 are n-side electrodes, respectively.

In this semiconductor light receiving device, by providing the mesa groove 5 for separating the elements from each other, carriers generated by the light incident on a certain element do not enter the adjacent element, It prevents the occurrence of cross talk.

[0008]

In the semiconductor light receiving device shown in FIG. 6, the mesa groove 5 is formed in order to prevent cross talk. Normally, in this type of semiconductor light receiving device. In order to increase its photosensitivity, n-InGa
Since the As light absorption layer 3 is thickened, for example, 2 [μm] to 3 [μm], the depth of the mesa groove 5 is about 5 [μm] to 6 [μm].
m]. Therefore, due to the step difference of the mesa groove 5, various problems such as the step difference of the antireflection coating film 7 occur.

According to the present invention, by adopting an extremely simple means, the diffusion length of carriers at the hetero interface is shortened, the diffusion of carriers generated by incident light is suppressed, and the occurrence of cross talk is suppressed. Try to prevent.

[0010]

FIG. 1 is a cutaway side view of an essential part of a semiconductor light receiving device for explaining the principle of the present invention, and the same symbols as those used in FIG. 6 represent the same parts. Or have the same meaning.

The semiconductor light receiving device shown in FIG. 1 differs from the semiconductor light receiving device shown in FIG. 6 in that the n-InGaAs light absorption layer 3 to be subjected to photoelectric conversion is 1 × 10 ¹⁷ [cm].
^-3 ]] About 500 containing high concentration of impurities
Thin n ⁺ -InGaAs of about [Å] to 1000 [Å]
It is located between the carrier diffusion suppressing layers 11 and 12.

With such a structure, n-InGaA
s light absorption layer 3 and n-InP buffer layer 2 or n-In
The carrier diffusion length at the hetero interface with the P window layer 4 becomes short.

From the above, in the semiconductor light receiving device according to the present invention, (1) the forbidden band widths E _g1 and E _g2 and E _g3 have a relationship of E _g1 > E _g2 and E _g3 > E _g2. The first compound semiconductor layer of one conductivity type (e.g., n-InP buffer layer 2) having a forbidden band width of E _g1 and having a forbidden band width of E _g2 that are present and are sequentially stacked to form a heterojunction structure. One conductivity type second compound semiconductor layer (for example, n-InGaAs light absorption layer 3) and one conductivity type third compound semiconductor layer (for example, n) having a forbidden band width of E _g3.
-InP window layer 4) and a forbidden band width of E _g2 inserted at each hetero interface in the heterojunction structure and having a sufficiently high concentration of one conductivity type as compared with the second compound semiconductor layer. Compound semiconductor thin film containing impurities (for example, n ⁺ −
InGaAs carrier diffusion suppression layers 11 and 12) and a plurality of opposite conductivity type impurity diffusion regions (for example, p ⁺ − window region 6) arranged in parallel while maintaining a depth reaching a second compound semiconductor layer from the surface and a predetermined interval. Or comprising, or

(2) In the above (1), the first compound semiconductor layer, the second compound semiconductor layer, and the third compound semiconductor layer are InP layers, InGaAs layers, and InP layers. .

[0015]

According to the above-described structure of the present invention, InGaAs
Since the InGaAs layer having a high impurity concentration is interposed between the InP layer and the InP layer, the diffusion length of carriers at the hetero interface is shortened, and effective photosensitivity is achieved without forming a mesa groove. Since the area of the device is reduced, cross talk between the elements is reduced.

FIG. 2 is a diagram showing the photosensitivity in the case where the semiconductor light receiving device is irradiated with spot-like light and one-dimensionally scanned, and the photosensitivity is plotted on the vertical axis and the position is plotted on the horizontal axis. It is taken. In the figure, PC1 and PC2 respectively indicate the light receiving element portion, the broken line is the characteristic line in the case where the n ⁺ -InGaAs carrier diffusion suppressing layer is present (the present invention), and the solid line is the n ⁺
The characteristic lines in the case where there is no -InGaAs carrier diffusion suppression layer (experimental example) are shown.

As is apparent from the figure, the light receiving element portion PC
The photosensitivities of the light receiving element portions PC1 and PC2 are the same as those of the present invention and those of the experimental example.
In the meantime, in the case of the present invention, the value is zero in the center of the present invention, but it is observed that the experimental example has a considerable photosensitivity, and the effect of the present invention is clear.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 3 to 5 are side sectional views of essential parts of a semiconductor light receiving device at a process step for explaining a process for manufacturing an embodiment of the present invention. The details will be described. The same symbols as those used in FIGS. 1 and 6 represent the same parts or have the same meanings.

See FIG. 3 3- (1) Vapor phase epitaxial growth
pitaxy: VPE) method depends on applying the, n ⁺
N-InP buffer layer 2, n ⁺ -I on -InP substrate 1
nGaAs carrier diffusion suppression layer 11, n-InGaAs
Light absorption layer 3, n ⁺ -InGaAs carrier diffusion suppression layer 1
2. Grow the n-InP window layer 4.

The main data regarding each semiconductor layer grown here is illustrated as follows. About the buffer layer 2 Thickness: 1 [μm] Impurity concentration: 1 to 2 × 10 ¹⁶ [cm ⁻³ ] About carrier diffusion suppression layer 11 Thickness: 500 [Å] to 1000 [Å] Impurity concentration: 1 to 5 × 10 ¹⁷ [cm ^-3 ]

Regarding the light absorption layer 3 Thickness: 2 [μm] to 2.5 [μm] Impurity concentration: 1 to 5 × 10 ¹⁵ [cm ⁻³ ] Carrier diffusion suppressing layer 12 Thickness: 500 [Å] to 1000 [Å] Impurity concentration: 1 to 5 × 10 ¹⁷ [cm ⁻³ ] Regarding the window layer 4 Thickness: 0.5 [μm] to 1 [μm] Impurity concentration: 5 to 10 × 10 ¹⁵ [cm ⁻³ ]

See FIG. 4 4- (1) Plasma CVD (plasma chemical v)
The SiN _x film 13 having a thickness of, for example, 2000 [Å] is formed by applying the apour deposition method. 4- (2) The SiN _x film 13 is selectively etched by applying a resist process in the lithography technique and a wet etching method using an etchant as a mixed liquid of hydrofluoric acid and ammonium fluoride. Then, the window region forming opening 13A is formed.

4- (3) By applying the thermal diffusion method, the temperature is 500 [° C.],
Then, the time is set to 15 minutes, the zinc phosphide diffusion source penetrates the n ⁺ -InGaAs carrier diffusion suppression layer 12 from the surface of the n-InP window layer 4 through the window region forming opening 13A, and n- Zn is diffused to reach the InGaAs light absorption layer 3 so that the impurity concentration is 1 × 10 ¹⁸ [cm
^The p ⁺ -window region 6 having a size of about ⁻³ ] is formed.

See FIG. 5 5- (1) By applying the plasma CVD method, the thickness is, for example, 2
The anti-reflection coating film 7 made of SiN _{x of} 000 [Å] is formed.

5- (2) By applying a resist process in the lithography technique and a wet etching method using an etchant as a mixed solution of hydrofluoric acid and ammonium fluoride, the antireflection coating film 7 is formed. Selective etching is performed to form a p-side electrode contact window. 5- (3) Thereafter, a normal technique such as a vacuum vapor deposition method and a lift-off method is applied to apply the p-side electrode 8 made of AuZn or Au.
The n-side electrode 9 made of Ge is formed and completed.

According to the principle described with reference to FIG. 1, the semiconductor light-receiving device thus obtained does not cause cross talk even if the mesa groove is not formed, and of course the surface is flat.

[0027]

In the semiconductor light receiving device according to the present invention, the forbidden band widths E _g1 and E _g2 and E _g3 have a relationship of E _g1 > E _g2 and E _g3 > E _g2 and are formed in order. Forming a heterojunction structure, the first conductivity type first compound semiconductor layer having a forbidden band width of E _g1 and the second conductivity type second compound semiconductor layer having a forbidden band width of E _g2 and the forbidden band width E _A third conductivity type third compound semiconductor layer of _g3 and a forbidden band width of E _g2 which is inserted at each hetero interface in the heterojunction structure and is sufficiently compared with the second compound semiconductor layer. A compound semiconductor thin film containing a high concentration of one conductivity type impurity, and a plurality of opposite conductivity type impurity diffusion regions arranged in parallel while maintaining a depth reaching a second compound semiconductor layer from the surface and a predetermined interval.

According to the structure of the present invention, for example, between the first compound semiconductor layer which is a buffer layer and the second compound semiconductor layer which is a light absorption layer, and between the second compound semiconductor layer and the window layer. Since a compound semiconductor thin film which is the same material as the second compound semiconductor layer and which is a carrier diffusion suppressing layer having a high impurity concentration is present between the third compound semiconductor layer which is The diffusion length of carriers in the carrier can be shortened, and the area having an effective photosensitivity becomes narrower without forming a mesa groove as in the conventional case, and cross talk between elements can be reduced. Further, since the mesa groove is not formed, there is no large step, and therefore various problems caused by the step, such as step breakage of the antireflection coating film, can be solved.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a main part of a semiconductor light receiving device for explaining the principle of the present invention.

FIG. 2 is a diagram showing photosensitivity when a semiconductor light receiving device is irradiated with spot-like light and one-dimensional scanning is performed.

FIG. 3 is a side sectional view of a main part of a semiconductor light receiving device at a process key point for explaining a process for manufacturing an embodiment of the present invention.

FIG. 4 is a side sectional view of a main part of a semiconductor light receiving device at a process key point for explaining a process for manufacturing an embodiment of the present invention.

FIG. 5 is a cutaway side view of a main part of the semiconductor light receiving device at a process key point for explaining a process for manufacturing the embodiment of the present invention.

FIG. 6 is a cutaway side view of a main part showing a conventional example of a semiconductor light receiving device having a structure for preventing cross talk.

[Explanation of symbols]

Anti-reflective coating film composed of a window region 7 SiN _x - 1 n ⁺ -InP mesa groove 6 for separating between the substrate 2 n-InP buffer layer 3 n-InGaAs light absorbing layer 4 n-InP window layer 5 element p ⁺ 8 p-side electrode 9 n-side electrode 11 n ⁺ -InGaAs carrier diffusion suppression layer 12 n ⁺ -InGaAs carrier diffusion suppression layer 13 SiN _x film 13A opening PC1 light receiving element portion PC2 light receiving element portion

Claims (2)

[Claims] 1. The forbidden band widths E _g1 and E _g2 and E _g3 are in a relation of E _g1 > E _g2 and E _g3 > E _g2 and are formed in order to form a heterojunction structure. One conductivity type first compound semiconductor layer having _g1 and one conductivity type second compound semiconductor layer having a forbidden band width E _g2 and one conductivity type third compound semiconductor having a forbidden band width E _g3 And a compound having a forbidden band width of E _g2 interposed at each hetero interface in the heterojunction structure and containing a sufficiently high concentration of one conductivity type impurity as compared with the second compound semiconductor layer. A semiconductor light receiving device comprising: a semiconductor thin film; and a plurality of opposite-conductivity-type impurity diffusion regions arranged in parallel while maintaining a depth reaching a second compound semiconductor layer from the surface and a predetermined interval. 2. The first compound semiconductor layer, the second compound semiconductor layer and the third compound semiconductor layer are InP layers and InG.
2. An aAs layer and an InP layer.
Described semiconductor light receiving device