JPS6354778A - Infrared ray detector - Google Patents

Abstract

PURPOSE:To obtain an infrared ray detector which has less leakage current due to dislocation based on an irregular lattice by adding an impurity for suppressing the dislocation of the irregular lattice at either one or both of an Hg1-xCdxTe layer for forming a P-N junction and an Hg1-yCdyTe layer formed on the surface. CONSTITUTION:An Hg1-yCdyTe layer 3 having large X value is formed on the surface of an Hg1-xCdxTe substrate 1 or the peripheral region of a P-N junction 2-1 of a photoelectric converter. An impurity for suppressing the movement of the dislocation of the irregular lattice is added to either one or both of the surface layer of the substrate 1 or the layer 3. For example, after a masking film 1-1 is formed on the P-N junction region of the substrate 1 doped with Zn for suppressing the movement of the dislocation. an Hg1-yCdyTe crystal 3 having large X value is formed. A mutual diffused layer 4 is formed during the crystal growth. Then, B ions are implanted to form an N-type layer 2, a zinc sulfide ZnS 5 which becomes an insulating layer is formed on the surface, opened with a predetermined hole, and an In electrode 6 contacted with the layer 2 is formed, thereby obtaining an infrared ray detector.

Description

[Detailed Description of the Invention] [Summary] In order to reduce the surface leakage current at the PN junction of an infrared detector using a Hg, -xcdxTe crystal that detects infrared rays with high sensitivity, lattice misalignment dislocations are created throughout the interdiffusion layer. In order to prevent the occurrence of lattice misalignment, impurities are used to inhibit the movement of lattice misalignment dislocations.

[Industrial application field]

This invention relates to photovoltaic infrared detectors, especially Hg, XC
This invention relates to an infrared detector using a dxTe crystal as a substrate.

Infrared detectors are manufactured using compound semiconductor crystals such as Hg, -xcdXTe crystals, which detect infrared rays with high sensitivity, as substrates. This infrared detector has multiple elements, and in order to maintain high sensitivity, each infrared detecting element is required to have a small surface leakage current.

[Conventional technology]

Surface leakage currents that affect the characteristics of electromotive force type infrared detectors using PN junctions include band-to-band tunneling currents and tunneling currents associated with crystal defects such as dislocations. The interband tunneling current is caused by the HgI-xCdxT forming the substrate.
It is related to the energy gap εg of the e-crystal, and the larger the energy gap εg, the smaller the tunnel current.

Therefore, an infrared detector having the structure shown in FIG. 3 is created. That is, p-Hg, -xCdxTe crystal substrate 1
A Hg+-yCdy Te crystal layer 3 having a large X value is formed outside the region on the surface where the PN junction is to be formed.

When crystal growth of such a two-layer structure is performed, an interdiffusion layer 4 is inevitably generated at the boundary between the two layers. This mutual diffusion layer 4
is a region where the X value is larger than that of the Hg+-xCdx Te layer, and the energy gap εg is wide (which reduces surface leakage current due to interband tunnel current).

FIG. 4 shows a case where Hg, Cd, and Te'R3 are formed on the surface of a P-HgsxCdxTe crystal substrate 1, and then eight layers 2 are formed.

In any case, the locations where lattice misalignment dislocations exist are spread throughout the interdiffusion layer 4.

[Problem that the invention seeks to solve]

The conventional infrared detector described above reduces the interband tunneling current at the surface, but since lattice mismatch points are distributed throughout the interdiffusion layer, the PN junction becomes P-Hg+-xCd.
There is also a location where there is a high density of lattice misalignment at the location where it intersects with the interface between the x Te crystal 1 and the interdiffusion layer 4, and there is a problem in that the leakage current associated with dislocations due to the lattice misalignment increases at this location. .

SUMMARY OF THE INVENTION In view of the above-mentioned conventional situation, it is an object of the present invention to provide an infrared detector that generates less leakage current due to dislocations caused by lattice misalignment.

[Means for solving problems]

In this invention, I1g+-xCd forming the PN junction
xTe layer and Hg+-yCdy formed on its surface
The structure is such that impurities are added to one or both of the TeFi to inhibit the movement of lattice misaligned dislocations.

[Effect]

Even if the crystal is diffused, the locations where lattice misalignment dislocations are distributed will be
Since the impurities that suppress dislocations do not spread throughout the interdiffusion layer, there are no lattice misalignment dislocations at the position where the PN junction intersects the interface between the )Ig+-xCdxTe crystal and the interdiffusion layer, and the lattice misalignment dislocations Leakage current is prevented.

〔Example〕

FIG. 1 is a cross-sectional view for explaining the infrared detector of the present invention. As shown in Figure 1 fa), P-Hg+-xCd doped with zinc (Zn) to inhibit dislocation movement.
A masking film 1 is placed on the PN junction region of the xTe crystal substrate 1.
After adding -1, Hg+-yCdy Te with large X value
A crystal 3 is formed to form the state shown in FIG. 1(b).

During crystal growth, an interdiffusion layer 4 is formed as shown in FIG. 1(C). Even if interdiffusion occurs, the distribution locations of lattice misaligned dislocations (indicated by P4g+- before Tei formation
It remains at the surface of the yCdy Te crystal substrate.

This addition of Zn inhibits the movement of dislocations because
This is because the bond energy between Zn and Te is larger than the bond energy between Hg and Te or Cd and Te atoms that constitute the crystal.

In this state, boron iB atoms are ion-implanted into the region where the PN junction is to be formed to form eight layers 2. Here the PN junction is designated 2-1. Therefore, the PN junction 2-1 is P
-Hg+-xCdx Since no lattice misalignment exists at the location where the Te layer intersects with the boundary between the interdiffusion layer, leakage current due to dislocations due to lattice misalignment can be prevented.

Further, as shown in FIG. 1 (dl), zinc sulfide ZnS 5 is formed on the surface to serve as an insulating layer, and an indium In electrode 6 is formed in contact with the 8 layer 2 by opening it in a predetermined manner. A detector is obtained.

FIG. 2 is a sectional view of main parts showing another embodiment, p-n
g, -xCaxTe crystal layer is doped with Zn to form Hg+
Ni2 is formed after the -yCdyTe crystal 3 is formed, and this also has the same effect as the above-mentioned embodiment.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, H
By simply adding an impurity to one or both of the g+-xCdx Te crystal and the Hg1-, Cd, or Te crystal to suppress the movement of lattice misalignment dislocations, a highly sensitive infrared detector with low leakage current can be obtained. This has an extremely effective effect in improving quality.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the main part of an example of an infrared detector according to the present invention, Fig. 2 is a sectional view of the main part showing another embodiment of the invention, and Fig. 3 is a sectional view of a conventional infrared detector. A first main part sectional view for explaining the crystalline state. FIG. 4 is a second main part sectional view for explaining the crystalline state of a conventional infrared detector. In the figure, 1 is a p-Hg, -xCdxTe antagonistic substrate, 2 is an N layer, and 3
4 indicates a Hg, yCdyTe crystal, and 4 indicates an interdiffusion layer. /1 Figure 1 of potato flakes vinegar side 6t'a? 1st day of dawn moon tori attack〉Healing summoning trick 9 request T1 attached to door i$il
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Claims (1)

[Claims] Mercury, cadmium, tellurium (Hg_1_-_xCd_x
Te) The surface of the substrate (1) or the PN which is the photoelectric conversion part
Hg_1_ with a large x value in the surrounding area of the joint (2-1)
-_yCd_yTe layer (3) In the infrared detector formed by forming the Hg_1_-_xCd_xTe substrate (
1) surface layer or the Hg_1_-_yCd_yT
An infrared detector characterized in that one or both of the e-layers (3) are doped with impurities that inhibit the movement of lattice misalignment dislocations.