JPH01228180A - Infrared ray detecting element - Google Patents

Abstract

PURPOSE:To prevent the generation of a cross-talk by a method wherein an island-like mutual diffusion layer is formed on a super lattice layer of mercury telluride and cadmium telluride, and a P-N junction is provided in a region corresponding to the mutual diffusion layer of a compound semiconductor layer on the super lattice. CONSTITUTION:A super lattice layer 12 of HgTe and CdTe is formed on a substrate 11, which is subjected to a heat treatment to form a island-like mutual diffusion layer 13 of a crystalline layer of HgTe and CdTe. Moreover, an element forming crystalline layer 14 is provided to the super lattice 12 and an element forming P-N junction 15 is provided inside the crystalline layer 14 corresponding to the mutual diffusion layer 13. In result, the light rays incident onto a position between elements in horizontal direction are absorbed by light rays incident from the rear of a substrate 11 and carriers photoelectrically converted at the position are recombined at the part of the super lattice layer 12 narrow in an energy gap so as not to reach the element of the P-N junction 15. By these processes, the generation of a cross talk can be prevented.

Description

[Detailed Description of the Invention] [Summary] The present invention is applied to a multi-element type photovoltaic infrared sensing element, and is intended to prevent crosstalk from occurring in signals processed by the sensing element. An island-shaped interdiffusion layer of the superlattice layer is formed in the superlattice layer of mercury/tellurium and cadmium/tellurium, a compound semiconductor layer is provided on the superlattice layer, and the interdiffusion layer of the compound semiconductor layer is formed. It is constructed by forming an element by providing a P-N junction in a region corresponding to the layer.

[Industrial application field]

The present invention relates to an infrared sensing element, and particularly to a multi-element photovoltaic infrared sensing element.

An infrared sensing element is formed using a mercury-cadmium-tellurium (Hg+-xcdx Te) crystal with a narrow energy band gap, and in order to obtain a high-resolution image with this sensing element, the crystal is A multi-element type infrared sensing element in which a large number of infrared sensing elements are arranged in an array has been developed.

However, as elements are arranged at a higher density, the problem arises that crosstalk occurs in image signals processed by the elements when the distance between the elements becomes shorter than the diffusion length of photoelectrically converted minority carriers. It is desired to develop a device that solves this problem.

[Prior Art] The structure of a conventional multi-element photovoltaic infrared sensing element is shown in FIG.

As shown in the figure, the conventional infrared sensing element has P-type Hgl having mercury vacancies as acceptors on a compound semiconductor substrate 1 such as cadmium-zinc-tellurium (CdZnTe).
□Cdx A crystal layer 2 of Te is formed using a liquid phase epitaxial growth method or the like, and boron (B) atoms are ion-implanted into the crystal layer 2 in a predetermined pattern to form an N-type layer 3. A protective film 4 made of zinc sulfide (ZnS) is formed on the surface of the crystal layer 2, a window is opened on the N-type layer 3, and an electrode 5 is formed on the N-type layer 3 to form a multi-element type light. An electromotive force type infrared sensing element is formed at the P-N junction 6.
corresponds to one pixel.

[Problem to be solved by the invention]

When signal processing of infrared rays is performed using such a detection element, as shown in FIG.
The photoexcited carriers 7 photoelectrically converted in the CdXTe crystal layer 2 move in the directions of arrows B and C in both directions of the P-N junction 6 or the P-N junction 8 adjacent to the P-N junction 6. As a result, crosstalk between pixels occurs, making it impossible to capture high-resolution images.

The tendency for this crosstalk to occur is that in order to increase the resolution of non-life insurance images, the elements are arranged in a high density, and the distance between the elements is relative to the carrier diffusion length in the horizontal direction between the CP-N junctions. becomes larger as the distance becomes shorter.

The present invention aims to eliminate the above-mentioned problems and provide a high-quality infrared sensing element that does not generate crosstalk.

[Means to solve the problem]

As shown in FIG. 1, the infrared sensing element of the present invention has a substrate 1
An island-shaped mutual diffusion layer 13 of the superlattice layer is formed on the superlattice layer 12 of mercury/tellurium and cadmium/tellurium provided on the superlattice layer 1, and a compound semiconductor layer 14 is provided on the superlattice layer. A device is constructed by providing a PN junction 15 in a 6g region of the layer 14 corresponding to the interdiffusion layer 13.

(Function) The energy of the superlattice layer 12 is made by periodically laminating several 100 7 kS tellurium (Te) crystals to a thickness of SO using molecular beam epitaxial growth, metal organic CVD (MOCVD), etc. The bandgap of both crystals, namely l1gTe and C
Hg+-x Cd formed by mutual diffusion of dTe crystals
, is smaller than the energy bandgap of the Te interdiffusion layer 13, and this superlattice layer region 12 does not transmit short wavelength light and carriers are easily recombined.

Therefore, a superlattice layer 12 of HgTe and CdTe is formed on the substrate.
is formed, and this superlattice layer 12 is heat-treated to form island-like l(g
Hg+-x CdX of Te and CdTe mutual diffusion layer 13
A crystal layer of Te is formed, and on this superlattice layer 12, a crystal layer 14 of ngl□Cd++ Te is further provided for forming an element.
x Cdx P-N for element formation in the Te crystal layer 14
By providing the bonding portion 15, light incident from the back side of the substrate is absorbed at a position between the elements in the horizontal direction, and carriers photoelectrically converted at that position are transferred to the narrow energy bandgap. Since they are recombined at the superlattice layer 12, they do not reach the elements at the PN junction 15, thereby eliminating crosstalk.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the infrared sensing element of the present invention is made of CdTe.
HgTe on the surface of the substrate or CdZnTe substrate 11
- The superlattice layer 12 made of CdTe is grown to a thickness of 5 μm by molecular beam epitaxial growth method or metal organic CVD method (M
The superlattice layer 12 is formed using a method such as laser annealing in a predetermined pattern to form HgTe.
and CdTe island-like interdiffused layer of Hg+-++ Cd.
A crystal layer 13 of Te is formed. Further, on this superlattice layer 12, a crystal layer 14 of l1g+-x Cdx Te for forming a P-type element using mercury vacancies as acceptors is formed, and a crystal layer 14 of Hgl-0CdTe for forming this element. B° atoms are ion-implanted into a region corresponding to the interdiffusion layer 13 to form an N-type layer 16, and a PN junction 15 is formed.

Further, a surface protection film 17 made of ZnS is formed on the substrate, and an electrode 18 made of In is provided with an opening on the N-type layer 16.

In order to form such an infrared sensing element, the steps shown in FIG.
), on the surface of a CdTe substrate or a CdZnTe substrate 11, an 11 g Te layer 12A with a thickness of 126 g and a CdTe crystal layer 12B with a thickness of 54 g were alternately and periodically subjected to molecular beam epitaxy and yellow growth. law or MOCVD
HgTe-
A CdTe superlattice layer 12 is formed.

Next, as shown in FIG. 2 [ex.], a metal mask 21 such as 〇 is placed on the substrate, and a static gas laser or the like is used to irradiate laser light along the direction of the arrow using the metal mask. Then, laser annealing was performed to mutually diffuse HgTe and CdTe, and the pitch was 30 μm and 20 μm x 20 μm.
A mutual diffusion layer 13 of Hg6.7 Cd5.3 Te with a thickness of about 1.5 m is formed in an island shape.

Next, as shown in FIG. 2(C), Hgo,z Cdo,z for forming a P-type element using mercury vacancies as acceptors is placed on the superlattice layer 12 provided with the formed interdiffusion layer 13.
A Te compound semiconductor crystal layer 14 is formed.

Next, B" atoms are ion-implanted into the region corresponding to the interdiffusion layer 13 in the element forming crystal layer 14 under the conditions of an acceleration voltage of 120 KeV and a dose of M1 x 1014/CT113 to form an N-type layer 16. After forming the N-junction 15,
As shown in FIG. 1, a protective film 17 made of ZnS is formed by vapor deposition, and then an electrode 18 made of In is formed by vapor deposition with an opening on the N-type layer 16 to form a multi-element type infrared sensing element. .

In this way, the crystal layer 13 of Hga, tCdo, 3Te formed by interdiffusion at a temperature of 77°
The energy bandgap of is about 0.25 eV, and the energy bandgap of the HgTe-CdTe1 lattice layer 12 is about 0.1eV. Therefore, the I1gTe-CdTe superlattice layer 12 with a narrower energy bandgap is better than the interdiffusion layer. of Hg. , 7 Cdo, 3 Te crystal layer 13 because carriers are more easily recombined in the substrate 11.
Among the infrared rays incident from the back surface of the PN junction 15, the light incident on the region located between the horizontal direction of the many formed P-N junctions 15 is absorbed, and at the same time, the carriers generated in that region are Since they are easily recombined and disappear in the grating layer 12, a highly reliable infrared sensing element with no crosstalk can be obtained.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a highly reliable multi-element infrared sensing element that does not cause crosstalk can be easily obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the element of the present invention, Fig. 2(a) to Fig. 2(C) are cross-sectional views showing the method of manufacturing the element of the present invention, and Fig. 3 is a cross-section of a conventional infrared sensing element. It is a diagram. In the figure, 11 is a substrate (CdTe substrate, ZnCdTe substrate), 12
) IgTe-CdTe superlattice layer, 128 is IIgTe
12B is a CdTe crystal layer, 13 is an interdiffusion layer (LLGO, 7CDO, 3Te crystal layer), 14 is a compound semiconductor crystal layer, 15 is a P-N junction, 16 is an N-type layer, 17 is a protection layer. 18 is an electrode, and 21 is a metal mask. Reikoro goes to 4th place? Fig.1
,,'l-,'Phantom Salmon Wa 1 Chisisuke Must Figure 3

Claims (1)

[Claims] Mercury, tellurium and cadmium provided on the substrate (11)
An island-shaped interdiffusion layer (13) of the superlattice layer is formed on the tellurium superlattice layer (12), a compound semiconductor layer (14) is provided on the superlattice layer, and a compound semiconductor layer (14) is formed on the superlattice layer (12). A P-N junction (15) is provided in a region corresponding to the interdiffusion layer (13).
) is provided to form an element.