JPH03148185A - Infrared detector - Google Patents

Abstract

PURPOSE:To prevent development of a lead current due to misfit transfer by forming a second semiconductor layer consisting of Cd, Hg, Te whose mixed crystal ratio (an x value) increases successively in a vertical direction of a first semiconductor surface consisting of CdxHg1-xTe. CONSTITUTION:A device is composed of a first semiconductor 1 of a small forbidden band width (a small x value), a second semiconductor layer 2 whose forbidden band width is larger than that of the first semiconductor 1 (x2>x1), an n<+>-layer 3, and a CdTe substrate 4. The second semiconductor layer 2 composed of Cd, Hg, Te whose mixed crystal ratio (an x value) increases successively is made to form in a vertical direction of a surface of the first semiconductor 1 which composed of CdxHg1-xTe. Since misfit transfer is not thereby generated at an interface between the first semiconductor 1 and the second semiconductor layer 2, a leak current in the area can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photovoltaic infrared detector using a semiconductor, and particularly relates to suppressing leakage current.

[Prior Art] FIG. 4 is a cross-sectional view of a conventional infrared detector disclosed in Japanese Patent Application Laid-Open No. 62-119975, in which (1) is a first semiconductor, (
2) is the second semiconductor, and in the forbidden cloth, the second semiconductor is higher than the first semiconductor.
Semiconductors have a larger structure. In photovoltaic infrared detectors, leakage current at the surface portion significantly reduces the performance of the detector. Furthermore, in the two-layer structure infrared detector, a large second semiconductor layer is formed in the forbidden cloth formed on the surface portion in order to suppress surface leakage current. However, manufacturing a two-layer structure by interdiffusion requires a complicated process, and it is difficult to control the composition.

Although it is a simple process to grow a second semiconductor layer with a large x4jli on the first semiconductor as it is, since semiconductors with different X values have different lattice constants,
Dislocations occur due to misfit at the interface between the semiconductor and the second semiconductor layer, and leakage current flows through the dislocations.

[Problems to be Solved by the Invention] In the above-mentioned infrared detector, the process for producing the two-layer structure is complicated, and since the process is performed at high temperatures, there is a problem with the uniformity of the composition of the first semiconductor. On the other hand, in the method of growing semiconductors with different X values.

a second semiconductor layer for controlling surface leakage current;
Due to the misfit transition that occurs at the interface with the semiconductor,
There were problems such as leakage current occurring in that part.

The object of the present invention is to suppress the generation of leakage current due to misfit transitions as described above, and to obtain an efficient infrared detector.

[Means for solving the problem] The infrared detector according to the present invention has Cd x Hg, -X
The mixed crystal ratio (x
(direct) increases continuously Cd, Hg.

A second semiconductor layer made of Te is grown.

[Function] The infrared detector in this invention has CdxHg1-x
Cd and Hg, the mixed crystal ratio (x value) of which increases continuously in the vertical direction of the first semiconductor surface made of Te.

Since the second semiconductor layer made of Te is grown, no misfit transition occurs at the interface between the first semiconductor and the second semiconductor layer, so that leakage current can be prevented at this portion.

[Example] An example of the present invention will be described below with reference to the drawings. FIG. 1(a) is a cross-sectional view of an infrared detector according to an embodiment of the present invention, in which (1) shows a first semiconductor with a small forbidden tea towel (small x value), and (2) shows a first semiconductor with a small forbidden tea towel. The second semiconductor layer (x2>x,) larger than the semiconductor, (3) is an n+ layer, and (4) is a CdTe substrate.

FIG. 1(b) is an explanatory diagram of FIG. 1(a). As shown in the figure, the composition of the second semiconductor layer changes continuously in the vertical direction, and the mixed crystal ratio (xs The value) was larger than the first semiconductor (7)X(tio,2) and was around 0.5.

As a manufacturing method for producing a Cd x Hg 1-xT e crystal having such a structure, a growth method using a slide boat method of the LPE method (liquid phase epitaxy) will be described.

Figure 2 shows the process. FIG. 2(a) is a cross-sectional view of the slide boat. The boat has a three-tiered structure, and semiconductor crystal growth is performed by sliding the upper and middle boats. FIG. 2(b) shows the position of each boat during the growth of the first semiconductor. to grow. The temperature is lowered from around 500℃, and the thickness is about 20μm.
After growing the first semiconductor, the upper boat is slid to open the upper part of the melt part, as shown in FIG. 2(c). This promotes the evaporation of I-I g' in the remelt, and the composition ratio of the melt changes continuously over time. Since the composition of the raw material melt moves in the direction of decreasing Hg, the second semiconductor N (Cdx2H
In the composition of gI

Moreover, C d xHg j- having the above structure
The method for growing XTe crystals is not limited to the slide boat method, but can also be realized by a tipping method using the same LPE method.

An example is shown in FIG. After the melt sealed in the ampoule is brought into contact with the substrate and the first semiconductor is grown, the ampoule is opened by removing the open end (11), thereby promoting the evaporation of Hg and forming the second semiconductor with a large X value. Grow layers.

- Cd with a similar structure can also be grown by such a growth method.
xHg, xTe crystals can be obtained.

[Effect of the invention] As described above, according to this invention, Cd XHg j−X
The mixed crystal ratio (x
C d , Hg , 'l' where the value) increases continuously
Since the structure is such that the second semiconductor layer made of E is grown, no crystal shift transition occurs at the interface between the first semiconductor and the second semiconductor layer, and a large Hg to Cd.

xTe semiconductor can be grown, and leakage current can be suppressed as an infrared detector.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of an infrared detector according to the present invention, FIG. 2 is a process diagram for manufacturing a CdxHg1-*Te crystal according to the present invention, and FIG. 3 is a process diagram of another embodiment of the present invention. , FIG. 4 is a sectional view of a conventional infrared detector. In the figure (1) is P-type Cd xHg, -xT e,
(2) is P-type Cd x2Hg 1-x2T e, (3)
is n+ layer, (4) is CdTe substrate, (5) is upper slide board, (6) is middle slide board, (7) is lower slide board, (8) is raw material melt, (9) is open hole, ( 10) is a quartz ampoule, and (11) is an open end. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In an infrared detector using a compound semiconductor made of Cd, Hg, and Te, the above Cd_xHg_1_-_xTe
In the vertical direction of the first semiconductor surface, the mixed crystal ratio (x value)
1. An infrared detector characterized in that a second semiconductor layer made of Cd, Hg, and Te is grown in which the diameter of the infrared rays increases continuously.