JPH0210117A - Infrared ray detecting element - Google Patents

Abstract

PURPOSE:To detect infrared rays in plural bands with one optical system by laminating 1st to 3rd semiconductor layers, whose widths of forbidden bands get wider and wider in order, in order of the 1st, 3rd and 2nd layers, radiating the infrared rays and absorbing the infrared rays in the 1st and the 2nd semiconductor layers. CONSTITUTION:The 1st, 3rd and 2nd semiconductor layers 16, 17 and 18 are laminated on a high-resistance substrate 1. By notching the parts of the 3rd and the 2nd semiconductor layers, a 1st electrode 19 is formed. Then, a 2nd electrode 20 and a light receiving surface 5 are formed on the 3rd semiconductor layer 18 with the technique of photomechanical process and the light receiving surface 5 is covered with a reflection preventing film. The widths of the forbidden bands of the semiconductor layers become wider in order of the 1st, 2nd and 3rd layers and the infrared rays absorbed in the 1st and the 2nd semiconductor layers 16 and 18 are detected by the 1st and the 2nd electrodes 19 and 20. Thus, the infrared rays near two bands, for example, the bands of 3 to 5mum and 10mum, can be detected with one optical system, thereby simplifying a device.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an infrared sensing element, and particularly to a photoconductive infrared sensing element that is sensitive to a plurality of wavelengths, for example, a 3 to 5 μm band and a 10 μm band. .

[Conventional technology]

FIG. 4fa) is a plan view showing the structure of a conventional photoconductive infrared sensing element, and FIG. 4(b) is a sectional view thereof.

Further, FIG. 5(a) is a plan view of a conventional infrared detection element having sensitivity in two wavelength ranges, and FIG. 5(b) is a sectional view thereof.

In the figure, 1 is a high-resistance substrate made of CdTe, and 2 is CdTe.
A semiconductor layer made of dXHg and □Te, 3 an electrode, 4 an antireflection film, and 5 a light-receiving surface. Also, 6 is a wavelength of 3 to 5 μm
7 is an infrared detecting element sensitive to a wavelength band of 10 μm, and 8 is a cooling substrate.

Next, a conventional infrared detection element will be explained using FIGS. 4 and 5.

CdXHg1-x Te is an IT-Vl group compound semiconductor, and the forbidden band width changes depending on the composition ratio X, especially x-0,2
Those with X = 0.3 are widely used as infrared sensing element materials for wavelengths of 3 to 5 μm. As a structure of an infrared detecting element using CdXHg1-XTe, a photoconductive type as shown in FIG. 4 is known. The photoconductive infrared sensing element is an element that detects infrared rays by changing the resistance value of the semiconductor layer 2 due to incidence of infrared rays. Such an infrared detection element is used in a device for image recognition of a target in combination with an optical system that mechanically scans space. FIG. 6 is a schematic diagram showing a device for image recognition of a target, where 9 is the field of view of the optical system, 10 is the instantaneous field of view, 11 is the optical system, 12 is the scanning device, 13 is the infrared detection element, and 14 is the signal processing The device 15 is a display device. By changing the position of the instantaneous field of view 10 by means of the scanning device 12, image recognition is possible even with a single element.

The infrared detection element 13 used in the above-mentioned devices is normally sensitive only to either the 10 μm band or the 3 to 5 μm wavelength band, but in order to improve the discrimination ability, it has been developed to have sensitivity in the two wavelength bands. It was desirable to have sensitivity to

For this reason, the conventional methods have been to use two infrared sensing elements each equipped with an optical system and a cooling system, each with a different wavelength range, or to arrange elements with different wavelength ranges in parallel as shown in Figure 5. A method was used that required only one optical system and cooling system.

[Problem to be solved by the invention]

Conventional infrared sensing elements use the methods described above to be sensitive to two wavelength ranges, so the method of using infrared sensing elements with two different wavelength ranges requires the optical system, cooling, etc. The problem is that there are multiple systems and the equipment becomes large, and the method of arranging elements with different wavelength ranges in parallel results in two focal points of the optical system, so it is necessary to attach the elements with great precision. Furthermore, even if the adhesive could be pasted with high precision, there was a problem in that sensitivity and resolution would inevitably deteriorate due to the nature of the wood.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain an infrared sensing element that is sensitive to a plurality of wavelength ranges.

[Means to solve the problem]

The infrared sensing element according to the present invention includes a first semiconductor layer that absorbs light in a first wavelength range, and a second semiconductor layer that absorbs light in a second wavelength range and has a wider forbidden band width than the first semiconductor layer. The semiconductor layer is formed in contact with the second semiconductor layer through a third semiconductor layer having a wider forbidden band width, so that infrared rays are incident from the second semiconductor layer side.

[Effect]

In this invention, the first
and a second semiconductor layer that absorbs light in a second wavelength range and has a wider bandgap than the first semiconductor layer through a third semiconductor layer that has a bandgap wider than the second semiconductor layer. Since they are formed in contact with each other and stacked vertically, the optical system only needs to focus at one point, which prevents deterioration in sensitivity and resolution.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 (Al is a plan view showing the structure of an infrared detecting element according to an embodiment of the present invention, and the crest in FIG. 1) is a sectional view thereof, and FIG. 2 is a perspective view thereof.

In the figure, 1 is a high-resistance substrate made of CdTe, 4 is an antireflection film, 5 is a light-receiving surface, and 16 is a CDO.

z Hgo, a first semiconductor layer consisting of a Te, 17
is the third cdXHg with X > 0.3, consisting of −+ Te.
, 18 is a second semiconductor made of Cdo, 3Hgo, and 7Te, 19 is a first electrode, 20 is a second electrode,
21 is infrared rays.

Next, the manufacturing process of the device of this example will be explained.

First, on a high-resistance substrate 1, for example, by liquid phase epitaxial growth, a first semiconductor layer 16 is formed to a thickness of about 10 to 20 μm, a third semiconductor layer 17 is formed to a thickness of about 1 to 3 μm, and a second semiconductor layer 1 is formed to a thickness of about 1 to 3 μm.
8 is sequentially formed to a thickness of about 10 to 20 μm, and then an antireflection film 4. By forming the second electrode 20, removing part of the second semiconductor layer 18 and the third semiconductor layer 17, and forming the first electrode 19 in the exposed part of the first semiconductor layer 16, The device shown in FIG. 1 is completed.

Next, the operation will be explained.

When infrared rays 21 are incident on the infrared sensing element according to the present example manufactured as described above, the infrared rays in the wavelength band of 3 to 5 μm are absorbed by the second semiconductor layer 18, and the infrared rays in the wavelength band of 10 μm are absorbed in the second semiconductor layer 18. 18, transmitted through the third semiconductor layer 17 and absorbed by the first semiconductor layer 16. Carriers generated in the first semiconductor layer 16 and carriers absorbed in the second semiconductor layer 18 are separated by a potential barrier created by the formation of the third semiconductor layer 17, as shown in FIG. , never mix. Therefore, the infrared rays absorbed by the first semiconductor layer 16 are detected by the first electrode 19, and the infrared rays absorbed by the second semiconductor layer 18 are detected by the second electrode 19.
Since the infrared rays are detected by the electrode 20, it is possible to independently detect infrared rays of two different wavelengths.

In the above embodiment, an infrared detection element sensitive only to two wavelength ranges, a 10 μm band and a 3 to 5 μm band, was described, but the present invention can also be applied to an infrared detection element having more wavelength ranges.

Furthermore, although the above embodiments have shown examples of single elements, they can also be applied to cases of multiple elements.

Furthermore, although the above-mentioned embodiment shows an example of a front-illuminated type, it is also possible to use a back-illuminated type by replacing the first semiconductor layer 16 and the second semiconductor layer 18.

〔Effect of the invention〕

As described above, in the infrared sensing element according to the present invention, the first semiconductor layer that absorbs light in the first wavelength range and the second semiconductor layer absorb light in the first wavelength range.
a second semiconductor layer having a wider forbidden band width than the first semiconductor layer that absorbs light in a wavelength range of is formed in contact with a third semiconductor layer having a wider forbidden band width than the second semiconductor layer; Since these are stacked vertically, the optical system only needs to focus at one point, and an infrared sensing element with high sensitivity and high resolution that is sensitive to a plurality of wavelength ranges can be obtained.

[Brief explanation of the drawing]

FIG. 1 fa) is a plan view showing the structure of an infrared sensing element according to an embodiment of the present invention, FIG. Band diagram for explaining the operation of the example, FIG. 4 (al is a plan view showing the structure of a conventional photoconductive infrared sensing element, FIG. 4 (bl is a cross-sectional view thereof, and FIG. 5 (al is a conventional FIG. 5 is a plan view of an infrared detection element sensitive to two wavelength regions (bl is a cross-sectional view thereof, and FIG. 6 is a schematic diagram showing an apparatus for image recognition of a target using an infrared detection element. , 1 is a high-resistance substrate, 4 is an antireflection film, 5 is a light-receiving surface, 16 is a first semiconductor layer, 17 is a third semiconductor layer, 18 is a second semiconductor layer, and 19 is a first electrode. , 20 is a second electrode. Note that the same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] (1) In a photoconductive infrared sensing element sensitive to a plurality of wavelength ranges, a first semiconductor layer that absorbs light in a first wavelength range;
A third semiconductor layer, which absorbs light in a second wavelength range, is laminated on the first semiconductor layer via a third semiconductor layer having a wider bandgap than the first semiconductor layer. and a narrow second semiconductor layer, the infrared rays detecting element being characterized in that infrared rays are incident from the first semiconductor layer side.