JPS62277774A - Manufacture of photoconductive semiconductor photodetector - Google Patents

Abstract

PURPOSE:To give high-speed response characteristics and high quantum-efficiency characteristics by removing electrodes on the surface of a light-absorption layer and applying an electric field through high concentration regions formed to a central section and an outer circumferential section so as to hold a ring- shaped low-concentration light-absorption carrier transit region. CONSTITUTION:n<+>-InGaAs except a columnar specific region is removed through reactive ion etching, using SiO2 film 3/resist film 4 ss masks, a photo-resist is gotten rid of, and n<->-InP 5 and n<->-InGaAs 6 are buried and grown. The SiO2 film 3 is taken off, an SiO2 film 7 is deposited anew, and the SiO2 film except the columnar specific region is removed through etching. Positioning is conducted so that the center of the circular form is made the same as the center of columnar n<+>-InGaAs 2. The n<->-InGaAs except the columnar specific region is gotten rid of through reactive ion etching, employing the SiO2 film 7/resist film 8 as masks. The photo-resist is taken off, and zn as an impurity is thermally diffused.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a photoconductive semiconductor light-receiving element used in optical communications, optical information processing, and the like.

[Conventional technology]

Compound semiconductor photodetectors are being actively researched, developed, and put into practical use as high-sensitivity photodetectors for optical communication or optical information processing. Among them, in the transit time limited mode of photoconductive semiconductor light receiving elements, the response time is determined by the carrier transit time, and the transit time and current gain are inversely proportional, so in the ultra-high speed region of Gb/s order or higher, the response time is determined by the transit time of the carrier. The 1.0-1.6 μm wavelength band, which is the low-loss band of optical fibers, is attracting attention as it has the potential to become a highly sensitive photodetector that replaces photodiode-type light-receiving elements. In this area, InGaAs is the most suitable material for the light absorption layer of a semiconductor photodetector. FIG. 3 shows an example of the basic structure of a conventional I n Ga AS photoconductive light-receiving element.
is formed by crystal growth, and further this n--I nGaA
It has an element structure in which two electrodes 11 and 12 are formed on the surface of the s-layer 6.

A voltage was then applied between these two electrodes to cause carriers to travel between them. Optical signals are converted into electrical signals by using the increase in conductivity caused by photoexcited carriers generated by light incident on the semiconductor surface.

[Problem that the invention seeks to solve]

In such a conventional structure, although an electric field is applied in the lateral direction (in a direction parallel to the semiconductor surface) in regions 13 and 14 where alloying between the electrode metal and the semiconductor is progressing near the semiconductor surface, the alloy is not progressing. In the deep region where there is no electric field, no electric field was applied to cause carrier 3 to travel. Therefore, carrier pairs (in Fig. 3,
The generation of carrier pairs is indicated by X, electrons are indicated by ○, and holes are indicated by As shown in FIG. 3, the carriers generated in the region must go through two processes: they diffuse to the region where the electric field is applied, and then they drift (indicated by the arrow - in the figure). This produces a slow component in the optical response, causing a tail of the pulse response.

In particular, for light in the 1.5 μm band, which is attracting attention in optical communications, InGaAs requires an absorption length of about 3 μrn in order to have sufficient sensitivity. The deterioration of the quantum efficiency due to the deterioration of the pulse response during the diffusion process or the disappearance of carriers due to recombination during the diffusion process has become impossible to ignore.

Furthermore, since the electrode metal is formed on the light absorption layer, the external quantum efficiency also decreases due to light shielding loss due to the electrode.

An object of the present invention is to provide a method for manufacturing a photoconductive semiconductor light-receiving element having high-speed response characteristics and high quantum efficiency characteristics, which overcomes these conventional drawbacks.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a photoconductive semiconductor light-receiving device, in which a high concentration compound semiconductor layer of the same conductivity type with a band gap E1 is crystallized on a conductivity type high concentration compound semiconductor substrate. The step of growing the high concentration semiconductor layer, and the step of removing this high concentration semiconductor layer leaving a specific cylindrical region, and forming a band gap E2 (>El) in the region other than the specific region - a low concentration compound semiconductor layer and band of the same conductivity type. The step of filling and growing a low concentration compound semiconductor layer of the same conductivity type, which is the gap E1, and this band gap E.

a step of removing the low concentration semiconductor layer leaving a columnar specific region having the same center as the columnar specific region; and a step of continuously diffusing a dopant to exhibit the same conductivity type. Features.

[Effect]

The present invention has solved the problems of the prior art by adopting the above-described configuration. In other words, in the photoconductive light-receiving element manufactured by this manufacturing method, an electric field is generated through the high-concentration region formed at the center and the outer periphery, sandwiching the ring-shaped low-concentration light-absorbing carrier traveling region. As a result, the electric field is applied uniformly in the depth direction of the semiconductor, and carriers generated deep within the light absorption low concentration region also drift without undergoing a diffusion process. Therefore, the problem of deterioration of the pulse response caused by the diffusion process or a decrease in quantum efficiency due to the disappearance of carriers due to recombination during the diffusion process can be solved. Furthermore, since there is no electrode on the surface of the light absorption layer, there is no reduction in external quantum efficiency due to light shielding loss. In this way, high-speed response and high quantum efficiency characteristics can be achieved.

[Example 1 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) to (g) are schematic diagrams of the cross-sectional structure of an element at each stage for explaining the manufacturing process of an embodiment of the present invention,
Further, FIG. 2 is a schematic cross-sectional structural diagram of a photoconductive semiconductor light-receiving element obtained by the above manufacturing method.

First, as shown in FIG.
Deposit film 3. After that, through a photoresist process, as shown in FIG.
□Remove the film by etching. Using this S i 02 film 3/resist film 4 as a mask, reactive ion etching is performed to remove n"-I nGaA in areas other than the columnar specific area.
s is removed ((C) in the same figure). After that, the photoresist was removed and the n--InP5. Buried growth of n--InGaAs6 is performed (FIG. 4(d)). Next, the 5i02 film 3 is removed, a new 5i02 film 7 is deposited, a photoresist process is performed, and the Si02 film other than the circular specific area is removed by etching, as shown in FIG. 3(e). At this time, the center of this circle is n''-I n
Align it so that it is the same as the center of GaAs 2. Then, in the same manner as in step (C) above, this 5i
Using the 02 film 7/lugist film 8 as a mask, reactive ion etching is performed to remove n--In except for the columnar specific area.
GaAs is removed ((f) in the same figure). Next, after removing the photoresist, impurity thermal diffusion of Zn (or Cd, etc.) is performed to form n"-I nGaAs 9.n"-InPl.
o is obtained ((g) in the same figure). Then n4-InP10
An electrode 11 is formed in a specific region on the substrate, and the back surface of the substrate is further polished to form a back electrode 12 to obtain a final device structure as shown in FIG.

In the above manufacturing process (by using reactive ion etching), the cylindrical InGaAs regions 2 and 6 can be processed with excellent verticality.
n"-TnGaA s 2 buried inside with a light-absorbing carrier transport layer of nGaAs6 in between, and n"I n GaA formed by impurity diffusion on the outer periphery.
By applying a voltage to s9, n--I n
A structure was obtained in which a uniform electric field could be applied in the depth direction of the light-absorbing carrier traveling region of GaAs6. As a result, photoexcited carriers generated in a deep part do not drift after undergoing a diffusion process to the upper layer where an electric field is applied, unlike in conventional elements, and the generated photoexcited carriers can be transferred regardless of the location where they are generated. It is immediately attracted by the electric field and drifts (in Figure 2, as in Figure 3, × indicates carrier pair generation,
O indicates an electron and ■ indicates a hole). Therefore, it has become possible to eliminate response deterioration and quantum efficiency reduction caused by the carrier diffusion process. In addition, in this structure, the electrodes are formed on the top and back surface of the n"-InPlo outside the light-receiving region, and are not present on the back surface of the light absorption layer of n--InGaAs 6. Therefore, the external quantum efficiency due to light shielding loss is reduced. It is now possible to prevent this from happening.

〔Effect of the invention〕

As explained above, according to the present invention, a method for manufacturing a photoconductive semiconductor light-receiving element having high-speed response characteristics and high quantum efficiency characteristics can be obtained.

[Brief explanation of the drawing]

FIGS. 1(a) to (g) are schematic cross-sectional structural diagrams showing an example of the manufacturing method according to the present invention in the order of steps, and FIG. 2 is a schematic diagram showing the structure of an element obtained by the above example. FIG. 3 is a schematic cross-sectional view of a conventional device. 1-n''-InP substrate, 2-n''-InGaAS, 3
, 7... 5i02 film, 4.8... Regis I, 5-
--n"'-InP, 6--n--I nGaAs,
9...n"-I nGaAs, 10-n"-I
n P, 11°12... Electrode, 13.14... Alloy progressing region, 15... Semi-insulating InP substrate. - Pe Agent Patent Attorney Uchihara A, R Hou 2 Figure 1 1I)/

Claims (1)

[Claims] a step of crystal-growing a high-concentration compound semiconductor layer of the same conductivity type with a band gap E_1 on a high-concentration compound semiconductor substrate of one conductivity type; a step of removing the high-concentration semiconductor layer leaving a columnar specific region; burying and growing a low concentration compound semiconductor layer of the same conductivity type with band gap E_2 (>E_1) and a low concentration compound semiconductor layer of the same conductivity type with band gap E_1 in a region other than the specific region;
a step of removing the low concentration semiconductor layer having the band gap E_1, leaving a columnar specific region having the same center as the columnar specific region; and a step of continuously diffusing a dopant to exhibit the same conductivity type. 1. A method for manufacturing a photoconductive semiconductor light-receiving element, comprising: