JPS62137872A - Infrared ray detector - Google Patents

Abstract

PURPOSE:To improve the sensitivity of a photoconductive type infrared ray detector by a method wherein a fixed number of narrow voltage measuring electrodes, having a highly-doped region on the circumference, are provided on the edge of the light-receiving part located in the vicinity of the other electrodes of fixed number, to be used to run a bias current, on the part separated from the latter, and the noise generated on the two electrodes used to run the bias current is suppressed. CONSTITUTION:Besides electrodes 1 and 2, narrow voltage measuring electrodes 3 and 4 which are separated from said two electrodes are provided on the edge of a light-receiving part 5 located in the vicinity of said electrodes on the circumference of a highly-doped region 11 in order to prevent the shortening of life of the excessive minority carrier. At this time, the amperage 1/f noise caused by the recombination of the carrier can be prevented by the electrodes 1 and 2 by picking out the potential difference between narrow voltage measuring electrodes 3 and 4 having highly-doped region 11 on the circumference, and the shortening of life of the excessive minority carrier can also be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an infrared detector, and particularly to a low impedance photoconductive infrared detector.

[Conventional technology]

Conventionally, this type of photoconductive infrared detector has been constructed as shown in FIG. FIG. 3 is a block diagram showing an example of a conventional photoconductive infrared detector, which has two electrodes 1.2 for passing a bias current, and which uses infrared radiation to
The potential difference proportional to the density of excess minority carriers generated in
cs) Volume 15, 1975, page 111).

[Problem that the invention seeks to solve]

In the conventional photoconductive infrared detector described above, due to current-based 17/f noise, which is said to be generated even in the electrodes,
There is a problem in that the larger the bias current Gf is, the more the sensitivity of the detector deteriorates in the low frequency region.

[Means for solving problems]

The infrared detector of the present invention includes two electrodes arranged at both ends of a light receiving section for flowing a bias current, and a region with a high doping amount arranged at both ends of the light receiving section and having a high doping amount. and two narrow voltage measurement electrodes.

[Effect]

FIG. 1(a) is a block diagram of a photoconductive infrared detector showing one embodiment of the infrared detector of the present invention, FIG. 1(b), (
c) are A-A′ and 113 in FIG. 1(a), respectively.
-B' sectional view.

In the figure, the same components as in the conventional example are given the same reference numerals as in FIG. 3. That is, in addition to the electrode 1.2, the photoconductive infrared detector of this embodiment has an electrode at the end of the light-receiving section 5, which is apart from and near both the electrodes 1 and 2, as shown in FIG. 1(a). It has narrow voltage measuring electrodes 3 and 4 surrounded by a highly doped region 11 in order not to reduce the lifetime of excess minority carriers.

Here, in order to obtain as large an output voltage as possible, electrode 1
．． A voltage measuring electrode 3.4 is provided as close as possible to the electrode 2.

Excess minority carriers generated in the light receiving part 5 by infrared radiation drift within the crystal between the electrodes due to the electric field applied to the electrodes 1 and 2.

Recombine at the interface and electrodes 1 and 2. When the electrodes 1 and 2 are used as voltage measurement electrodes, the carriers recombined at the electrodes 1 and 2 cause current-related 1/f noise.

Therefore, by collecting the potential difference between the narrow voltage measuring electrodes 3 and 4 surrounding the highly doped region 11 and amplifying it with the amplifier 6, the carriers are recombined at the electrodes 1-12. The resulting current-related 1/I noise can be avoided, and the lifetime of excess minority carriers can be prevented from decreasing. The reason for narrowing the width of the voltage measurement electrode 3.4 is to avoid reducing the number of carriers that flow toward the electrode per unit time and attempt to recombine, which causes noise. be. For example, in the four-terminal method used when measuring the pole coefficient, the widths of the four electrodes are usually the same. However, in this case, it is not possible to reduce ]/'f noise in photoelectric conversion.Next, the reason for providing the highly doped region 11 around the voltage measurement electrodes 3 and 4 is that between the region 11 and the crystal; In order to prevent excess minority carriers from approaching the voltage measurement electrodes 3 and 4 by creating a tensile gradient at J, that is, to prevent excess minority carriers from becoming short-lived due to recombination at the voltage measurement electrodes 3 and 4. It is. As a result, the so-called responsiveness value does not decrease as much as predicted by theory.

〔Example〕

Next, the present invention will be explained with reference to FIG.

FIG. 2(a) is a plan view showing one specific example in FIG. 1,
FIGS. 2(b) and 2(c) are sectional views taken along line AA' and line BB' in FIG. 2(ao), respectively.

As shown in FIG. 2<a), in this specific example, the electrode 1
, 2 is 765 B m, voltage measurement electrode 3
, 4 is 645 μm in length and 65 μm in width.

The thickness is 10 μm, and the width of the voltage measurement electrode 3.4 is 15 μm.
It is. The material of the photoconductive infrared detector is n-type Hg+)
The electrode was formed of 4Ci1g, 2Te single crystal 8 by vapor deposition or the like. Further, the 01 region 11 was formed by doping In by thermal diffusion or the like. As shown in FIGS. 2(b) and 2(c), this photoconductive infrared detector is bonded with adhesive 9 onto a sapphire substrate 10 with a thickness of 0.5 cm.

The solid angle of the aperture of this detector is 2.8 x JO-'s
r aperture and narrowband interference filter (center wavelength lO1
9μm, wavelength width 0.75μm.

Cooled to liquid nitrogen temperature with transmittance 75%), 7t ton background ~ IX10”ph
10-100 under the conditions of cys-2s-'
The sensitivity of the detector was measured in the 11z frequency range.

As a result of measuring noise in 1 mA increments in the range of 4 to 14 mA as a bias current, the 1/'f noise was approximately halved, while the subonshibidi was only reduced by approximately 10%. This means that the signal/7 noise ratio has been improved by about 1.8@. This allows the measurement time to be reduced to about ⅓.2 when obtaining a predetermined signal/noise ratio.

In other words, it is possible to perform more accurate measurements within a predetermined period of time.

Note that the present invention relates to the crystalline materials shown in the above examples.

Regardless of semiconductor type or wavelength band, in short, it is a photoconductive infrared detector that requires low impedance or a large bias current, such as a photoconductive infrared detector made of single crystal Pb5nTe. The present invention can also be applied to. Further, the substrate is not limited to a sapphire substrate as long as it has high thermal conductivity.

[Effects of the Invention J As explained above, the present invention provides, in addition to the two electrodes for passing the bias current, an electrode that is located at the end of the light-receiving section away from both electrodes and in the vicinity thereof, and does not reduce the lifetime of excess minority carriers. Therefore, by providing two narrow voltage measurement electrodes with a highly doped region around them, the 1/f noise generated by the bias current is suppressed and photoconductive infrared detection is achieved. This has the effect of improving the sensitivity of the instrument.

[Brief explanation of drawings]

FIG. 1(a) is a block diagram of a photoconductive infrared detector showing one embodiment of the infrared detector of the present invention, FIG. 1(b), (
c) are AA' and B- in FIG. 1(a), respectively.
B' sectional view, FIGS. 2(a and 2) are plan views showing one specific example in FIG. 1, and FIGS. 2(b) and (c) are respectively the second
The cross-sectional views taken along lines A-A' and B-B' in FIG. 1.2... Electrode, 3, 4... Voltage measurement electrode, 5.
... Light receiving section, 6... Amplifier, S...II g Cd
In T e, crystal, 9...adhesive, 10., sapphire substrate, 11... area. 1st word $ 2 flash (b) /θ (C)

Claims (1)

[Claims] Two electrodes placed at both ends of the light receiving section to flow a bias current, and two narrow voltages placed at both ends of the light receiving section at a distance from the electrodes and surrounded by a highly doped region. An infrared detector comprising a measurement electrode.