JPS60193375A - Semiconductor element - Google Patents

Abstract

PURPOSE:To enable to obtain an infrared charge injection element having a high-speed light-receiving characteristic by a method wherein P type conductive films, each having an energy gap smaller than that of an N type epitaxial layer provided on the substrate, are formed on the substrate corresponding to the positions of charge accumulation electrodes. CONSTITUTION:An N type Hg-Cd-Te epitaxial film 11 has been provided on an N type Hg-Cd substrate 10. Before this film 11 is formed, P type Hg-Cd-Te conductive films 12, each having an energy gap smaller than that of the film 11, are formed corresponding to the positions of charge accumulation electrodes 13. The incident lights of infrared rays are incided from the back surface side of the substrate 10 and a positive charge, which responded to an optical signal, is accumulated in potential wells 14 formed on the lower surfaces of the electrodes 13 whereon a negative charge is being impressed. This accumulated positive charge is injected in the direction of the substrate 10 from the electrodes 13 by impressing low voltage on charge injection electrodes 15 from the electrodes 13 and a signal is read. Lastly, a reset is performed. The positive charge is recombined in the films 12 right under the electrodes 15 at high speed at this time.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to the structure of a semiconductor device, and particularly to increasing the reading speed of a semiconductor device used in an infrared detector.

Background of the Technology In recent years, infrared radiation detection technology has developed, making it possible to measure the minute temperature distribution of objects even in cavities.

In particular, representative applications include infrared detectors for gas analysis for medical, industrial, scientific, and environmental management purposes, and infrared imaging devices that use the detected infrared signals as images. There is.

In these infrared detectors and infrared imaging devices, an infrared detection element receives infrared rays emitted by an object, converts this into an electric current, and detects minute temperatures.

Particularly in the case of infrared imaging devices, in the context of image scanning, infrared imaging requires an infrared sensing element to receive the projected infrared rays, convert it into an electric current, and read minute temperatures at high speed. This is necessary to improve the accuracy of the device, and its realization is desired.

tc+ Conventional technology and problems.

Types of infrared detection elements include In-5b infrared detectors made of indium (In) antimony (Sb) crystals, cadmium (Cd), mercury (Hg), and mercury (Hg), which have high sensitivity to wavelengths around 10 μm. Tellurium (Te
A Cd-1Cd-1l infrared detector using a crystal of ) as an infrared detection element is used.

In the present invention, a multi-element infrared detector in which several hundred infrared detecting elements are arranged in the case of a Cd-1Cd-1l ternary crystal will be described.

FIG. 1 is a sectional view of a conventional infrared sensing element.

In the figure, 1 is a Cd-Te substrate;
Te is transparent to infrared rays, 2 is a substrate electrode terminal, 3 is Cd-Hg-Te that constitutes an N-type semiconductor film, and 6 is a zinc sulfide (ZnS) film. It is an electrical insulator, and a charge storage electrode 4 and a charge injection electrode 5 are arranged on its upper surface.

In the case of multiple elements, the charge storage electrodes 4 of the respective elements are interconnected by a connection circuit 7. Similarly, the charge injection electrodes 5 of each element are connected to each other by a connection circuit 8.

In the figure, infrared rays are projected from the direction A, which is the back side of the substrate 1 of the infrared sensing element.

To explain the operation of the infrared sensing element now, the substrate is grounded and a negative voltage is applied to the charge storage electrode.

Under this charge storage electrode, carrier electrons are expelled through the insulating film 6 into the N-type Hg-Cd-Te film to form a depletion layer due to the negative voltage.

This depletion layer is electrically ground voltage N-type Hg-Cd-T
In the film of e, a negative voltage is applied, and a so-called potential well is formed.

This potential can be applied to the well by any suitable means, e.g.
This is a part where positively charged holes can be introduced and accumulated by methods such as emitting infrared rays.

In conventional back-illuminated charge injection devices, a negative voltage is applied to the charge storage electrode to form a potential and a well, and infrared rays are projected onto this part and an optical signal is used to fill the potential and well with positive charges. After accumulating holes, the potential I! is applied to the well by applying an appropriate voltage to the charge injection electrode. 77 boxes of positively charged balls are N
Inject into the Hg-Cd-Te film of the mold.

At this time, the projected infrared rays are detected by detecting the current generated by the movement of the injected charges.

However, after the injected charges move in this way and generate a current, it is preferable that the charges recombine and disappear instantly, but in reality, even if the charges become negative after readout, the injected charges injected into the substrate Charges cannot be recombined at a high speed, and charges remain.

In such a case, an infrared sensing element that performs readout at a high speed has the disadvantage that the residual charge is read out again, resulting in an error.

(d+ Object of the Invention In view of the above-mentioned drawbacks of the conventional art, an object of the present invention is to provide an infrared charge injection device having high-speed light receiving characteristics for use in an infrared detector.

lel Structure of the Invention According to the present invention, an N-type epitaxial film is provided on the upper surface of a compound semiconductor substrate, and a charge storage electrode and a charge injection electrode are arranged on the upper surface of the N-type epitaxial film. A back-illuminated charge injection device, which has P-type conductivity between the compound semiconductor substrate and the N-type epitaxial film, and has a smaller energy gap than the N-type epitaxial film. This can be achieved by providing a semiconductor element characterized in that a small epitaxial film is provided corresponding to the arrangement position of the charge storage electrodes.

(fl　Embodiments of the invention Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a cross-sectional view of an infrared charge injection device using an 11g-Cd-Te epitaxial crystal.

There is a Cd-Te substrate 10 forming an infrared charge injection device, and an N-type 11g-Cd-Te epitaxial film 11 is provided on the upper surface of the substrate 10. In the present invention, an N-type 11g-Cd-Te substrate 10 is formed.
Before forming the Te epitaxial MrA11, a P-type l1g-Cd-Te conductive film 12, which has a smaller energy gap than this N-type l1g-Cd-Te epitaxial layer, is formed in advance in accordance with the position of the charge storage electrode. It is done by forming.

Incident infrared light is incident from the back side of the Cd-Te substrate, and a positive voltage corresponding to the optical signal is generated in the potential well 14 formed on the lower surface of the charge storage electrode 13 to which a negative voltage is applied. Charge is accumulated.

The positive charge caused by the infrared signal is due to holes, and this accumulated positive charge is then applied to the charge injection electrode 15 with a voltage lower than the voltage of the charge storage electrode 13, so that the lower surface of the charge injection electrode After the charge is transferred to the potential well formed in , the accumulated signal charge is sequentially injected from the charge injection electrode toward the substrate one by one captured pixel bone, the signal is read, and finally the initialization is performed again. A reset is performed to return to the previous state.

During this signal reading and resetting, if the charges injected into the substrate recombine at high speed and disappear, the infrared charge injection device can operate at high speed.

The present invention provides a P-type l1g-Cd-Te film to inject the accumulated signal charges toward the substrate, read them, and then recombine the signal charges at high speed. The signal charge is transferred to the P-type l1g- directly below the charge injection electrode 15.
It is designed to be recombined at high speed with a Cd-Te film.

According to such a method, the amount of charge disappearing is about 1/10 compared to the conventional method.

In addition, since the 1) type IIg-Cd-Te film 12 is arranged, this part does not transmit infrared rays, so the incident infrared rays and the generated signal charges are transferred to the charge storage electrode 1.
Infrared rays incident around 3 are limited only to the charge storage electrode.

The reason why the P-type Hg-Cd-Te film 12 does not transmit infrared rays is that the energy gap of P-type-11g-Cd-TeH'J is smaller than the energy gap of the N-type Hg-Cd-Te epitaxial layer. This is because the infrared rays incident on this region are absorbed by the P-type 11g-Cd-Te film and cannot reach the N-type 11g-Cd-Te epitaxial film.

Regarding the energy gap, N-type 11g-Cd-T
In the case of e, it is 0.25e, v, and P-type Hg-Cd-
The Te film is 0', 15e, ν, and the difference is approximately 0.
．． Approximately 1e,v is optimal.

(Effects of the Invention As explained in detail above, by using the semiconductor element of the present invention, the readout speed of an infrared detector can be increased, and this infrared detector can be used as an imager of a highly accurate infrared detector. There is a great effect that it can be used for.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional infrared detector, and FIG. 2 is a sectional view of the infrared detector of the present invention. In the figure, 1.10 is a compound semiconductor substrate, 2 is a substrate electrode terminal, 3.11 is an N-type epitaxial film, and 4.1 is an N-type epitaxial film.
3 is a charge storage electrode, 5.15 is a charge injection electrode, 6 is an insulating film, 7.8 is a connection circuit, and 12 is P-type Hg-Cd-Te.
14 is a potential well. Figure 1 No. 21!1

Claims (1)

[Claims] An N-type epitaxial film is provided on the upper surface of a compound semiconductor substrate, and a charge storage electrode and a charge injection electrode are arranged on the upper surface of the N-type epitaxial film. An epitaxial film having P-type conductivity and having a smaller energy gap than the N-type epitaxial film is placed between the semiconductor substrate and the N-type epitaxial film corresponding to the arrangement position of the charge storage electrode. A semiconductor device characterized in that it is provided with a "ζ".