JPS63207183A - Photosensor - Google Patents

Abstract

PURPOSE:To control and change over spectral characteristics by forming an electrode on the side reverse to the side, to which beams are projected, in an intrinsic semiconductor region in a laterally shaped PIN photodiode and applying control voltage to the electrode. CONSTITUTION:An electrode 6 is formed onto a surface on the side reverse to the side, to which beams are projected, in a I semiconductor region 4 in a laterally shaped PIN photodiode. Consequently, the potential distribution of an electric field generated in the I region 4 can be changed by applying control voltage to the electrode 6. Potential distribution is altered largely by the magnitude of the control voltage, and the wavelength and photocurrent characteristics of the I region are varied by potential distribution. Accordingly, spectral characteristics can be controlled arbitrarily by control voltage applied to the electrode 6, and spectral characteristics can also be changed over by fluctuating control voltage.

Description

[Detailed description of the invention] The present invention will be described in the following order.

A. Industrial field of application B9 Summary of the invention C. Prior art [Figures 4 and 5] D6 Problems to be solved by the invention E1 Means for solving the problems F6 Effects G. Embodiments [First example] Figures to Figures 3] H1 Effects of the Invention (A. Field of Industrial Application) The present invention relates to a photosensor, and particularly to a photosensor in which a PIN photodiode is configured by a semiconductor region formed on an insulating substrate.

(B. Summary of the Invention) The present invention provides a semiconductor region formed on an insulating substrate.
In a photosensor configured as an IN photodiode, in order to fully control the spectral characteristics by voltage, P-type, intrinsic (1), and N-type semiconductor regions are arranged laterally on an insulating substrate. By forming a control electrode for controlling spectral characteristics via an insulating layer on the side of the I semiconductor region opposite to the side where the light is irradiated, the potential distribution in the I semiconductor region can be controlled by the voltage applied to the control electrode. It is designed so that it can be changed.

(C, Prior Art) [Fig. 4, Fig. 5] As shown in Fig. 4 as a photosensor, on an insulating substrate a made of quartz, for example, a P+ type semiconductor region b, a semiconductor region C, and an N+ type semiconductor region d are formed. Some PIN photodiodes are constructed by laminating (or forming laterally).

In such a photosensor, the spectral characteristics are usually adjusted by the film thickness t of the I region C, which is the photoelectric conversion section. This is because in a PIN photodiode, electron-hole pairs are generated within one region C by absorption of incident light, and I'? The depth at which incident light is absorbed in region A differs depending on the wavelength of the incident light, and becomes deeper as the wavelength becomes longer. Specifically, incident light belonging to the longer wavelength of visible light such as red and yellow enters I region C and is absorbed by I region C after traveling approximately 1 μm. Therefore, in order to obtain spectral characteristics that allow detection of incident light over the entire visible light band, the thickness of I region C should be J'X of 1 μm or more,
How to avoid detecting long wavelength light! The thickness of region C may be made thinner than 1 μm as appropriate. Therefore,
(2) Spectral characteristics can be controlled by the film thickness t of region C.

Figure 5 is a wavelength/absorption rate characteristic diagram showing how the absorption rate of incident light in I region C changes depending on the wavelength.This characteristic varies depending on the film thickness t of region C. It can be said that the spectral characteristics were controlled by utilizing the fact that the wavelength/absorption rate characteristics differ depending on the film thickness t of the I region C.

(D. Problems to be Solved by the Invention) By the way, there are various problems in controlling the spectral characteristics by controlling the film thickness t of region C. First, It is difficult to control, and variations tend to occur in the bonding properties that affect the spectral properties.Therefore, it is actually very difficult to control the spectral properties with high precision.

Furthermore, it was not possible to change the spectral characteristics of the odosensor after it was manufactured.

The present invention has been made to solve these problems, and it is possible to control with high precision the spectral characteristics of a photosensor of the type that constitutes a PIN photodiode by growing a semiconductor region on an insulating substrate. The purpose of this is to make the spectral characteristics variable.

(E. Means for Solving the Problems) In order to solve the above problems, the photosensor of the present invention has P-type, ■, and N-type semiconductor regions arranged laterally on an insulating substrate, and ■ It is characterized by forming an electrode for controlling spectral characteristics via an insulating layer on the side opposite to the side where the light is incident.

(F, action) According to the photosensor of the present invention, P formed laterally
An electrode is formed on the side opposite to the light incident side of the IN photodiode in the ■ region, so by applying a control voltage to that electrode, the potential distribution of the electric field generated in the I region can be changed. can be done. The potential distribution changes greatly depending on the magnitude of the control voltage, and the wavelength/charge current characteristics in the I region change depending on the potential distribution. Therefore, the spectral characteristics can be arbitrarily controlled by the control voltage applied to the electrodes, and the spectral characteristics can also be switched by changing the control voltage.

(G. Embodiment) [FIGS. 1 to 3] Hereinafter, the photosensor of the present invention will be described in detail according to the illustrated embodiment.

FIG. 1 is a sectional view showing one embodiment of the photosensor of the present invention.

In the figure, 1 is an insulating substrate made of quartz or the like, 2 is an N type semiconductor region formed on the surface of the insulating substrate 1, and 3 is a P type semiconductor region formed on the surface of the insulating substrate 1 at a distance from the semiconductor region 2. '' type semiconductor region 4 is an i type semiconductor region formed on a portion between the P+ type semiconductor region 3 and the N0 type semiconductor region 2, and has a film thickness of about 1 μm.

5 is an insulating layer formed on the surface of the I semiconductor region 4, and 6 is a control electrode for controlling spectral characteristics formed on the insulating layer 5.

This photosensor has a P+ type semiconductor region 3 grounded and an N
++ Applying a positive potential (+E) to the semiconductor region 2, and
A spectral characteristic control voltage Vg is applied between the control electrode 6 for controlling spectral characteristics and, for example, the P+ type semiconductor region 3.

FIG. 2 (A>, (B) shows the potential distribution on a plane cut at the center of the intrinsic semiconductor region 4.
The curve in the intrinsic semiconductor region 4 is an equipotential surface exposed at the cut surface. In the same figure (A), when the spectral characteristic control voltage Vg is OV, in other words, the electrode 6 is P+
The potential distribution is shown when the potential is the same as that of the type semiconductor region 3, and (B) shows the potential distribution when the spectral characteristic control voltage vg is +16
The case of V is shown.

When the spectral characteristic control voltage Vg is set to 0, the electric field due to the voltage applied between the N+ type region and the P+ type region is relatively high in the region 4, as shown in FIG. It's still alive. Therefore, light having a relatively long wavelength absorbed in the upper part of region 4 can also be converted into photocurrent. In other words, it is possible to apply an electric field to electrons and holes generated by long-wavelength incident light absorbed in the upper part of region 4, and to generate a photocurrent in the recombination portion. Therefore, the spectral characteristics can be made to detect even long wavelength light.

When the spectral characteristic control voltage Vg is increased (Vg=+1
6V) k: as shown in Figure 2 (B)! The lateral electric field caused by the reverse bias voltage E between the P+ type region and the N+ type region generated in the semiconductor region 4 is pushed downward by the depletion layer generated directly under the electric field Vi6, and as a result, the ■region 4
The electric field strength above becomes very weak. Therefore,■
Even if the light with a relatively long wavelength absorbed in the upper part of the region 4 is photoelectrically converted and electrons and holes are generated, the electrons are drifted to the spectral characteristic control electrode 6 which is given a positive potential.
It disappears at the end of its lifetime, and holes have a small lifetime and mobility, so they can hardly become a photocurrent. Therefore, almost no photocurrent is generated due to long wavelength light. The photocurrent flows only due to the short wavelength incident light absorbed in the lower part of the I region 4. Therefore, the spectral characteristics of the photosensor can be made to have narrow band characteristics that do not detect long wavelength light.

FIG. 3 shows the wavelength/photocurrent characteristics. From this figure, it can be seen that the characteristics can be changed by changing the spectral characteristic i (control voltage Vg) applied to the electrode 6. By continuously changing Vg, the wavelength and photocurrent characteristics can be changed continuously. Therefore, by adjusting the spectral characteristics control voltage Vg so that arbitrary wavelength and photocurrent characteristics can be obtained. Any spectral characteristic can be obtained with high precision.

-The spectral characteristics can be changed by switching the magnitude of the spectral characteristics control voltage Vg.

In this way, by making it possible to control the spectral characteristics of the photosensor with high precision, it is possible to enrich the functions of, for example, a copying machine, a facsimile machine, etc. using the photosensor. For example, if a report or the like is written on a document with red ruled lines and then copied and sent, the report can be copied and sent without the obtrusive ruled lines. Also,
By switching the spectral characteristic control voltage, for example, characters written in red can be copied or transmitted or not. In addition, letters written in Holeben have a tendency to diffusely reflect red light, making them difficult to read, so in order to make them easier to read, it is better to read them with a sensor with spectral characteristics that does not detect long wavelength light. This photosensor is ideal for use as such a sensor.

Moreover, a color filter can also be obtained by appropriately controlling the spectral characteristics.

Incidentally, the photosensor shown in FIG. 1 can be manufactured by the following method. A polycrystalline silicon layer having a thickness of, for example, about 800 nm is grown on an insulating substrate 1 made of quartz or the like by low pressure CVD, and the layer is once made amorphous by implanting Si4+ ions, and then grown at a temperature of 600°C. After improving the crystallinity of the layer by heat treatment, the portions of the layer that will become the N-type region 2 and the P-type head region 3 are covered with 5i02 or the like, and openings are provided on the other portions 4a. And S i H4 gas or 5iH2C
An amorphous silicon layer is selectively grown only on the opening at high temperature using a mixed gas of 12 and HCI, and this layer is used as the I semiconductor region 4.

Incidentally, this technique has already been proposed by the applicant company in Japanese Patent Applications Sho 61-144264 and Sho 61-144265. Thereafter, (1) an insulating layer 5 is formed on the surface of the semiconductor region 4 by a well-known method, and an electrode 6 is formed on the insulating layer 5.
is formed by vapor deposition or the like.

(H. Effects of the Invention) As described above, the photosensor of the present invention includes a first conductive type semiconductor region and a second conductive type semiconductor region which are spaced apart from each other on an insulating substrate; an intrinsic semiconductor region disposed between and connected to the second semiconductor regions, and an electrode formed via an insulating layer on the side opposite to the light incident side of the intrinsic semiconductor region; It is characterized by having the following.

Therefore, according to the photosensor of the present invention, since the electrode is formed on the side opposite to the light incident side of the intrinsic semiconductor region of the PIN photodiode formed laterally, a control voltage is applied to the electrode. This makes it possible to change the potential distribution of the electric field within the intrinsic semiconductor region. The potential distribution changes greatly depending on the magnitude of the control voltage, and the wavelength/charge current characteristics of the intrinsic semiconductor region also change depending on the potential component A11.

Therefore, the spectral characteristics can be arbitrarily controlled by the control voltage applied to the electrodes, and the spectral characteristics can be switched by changing the control voltage.

[Brief explanation of the drawing]

1 to 3 are for explaining one embodiment of the photosensor of the present invention, FIG. 1 is a cross-sectional view of the photosensor, and FIGS. 2(A) and 2(B) are inside the intrinsic semiconductor region. In the potential distribution diagram, (A) shows the case where the control voltage is Ov, and (,B) shows the case where the control voltage is 16V.
The figure is a wavelength/charge current characteristic diagram, Figure 4 is a sectional view showing a conventional example, and Figure 5 is a wavelength/absorption rate characteristic diagram showing that wavelength/absorption rate characteristics change depending on the thickness of the intrinsic semiconductor region. . Explanation of symbols 1... Insulating substrate, 2... First conductivity type semiconductor region, 3... Second conductivity type semiconductor region, 4... Intrinsic≠conductor region, 5... Insulating layer, 6... ··electrode. Wavelength/charge current characteristic diagram Figure 3 Conventional example tV diagram Figure 4 Heat absorption wavelength/0 small wave characteristic diagram Figure 5 Procedure Nefu official text (method) % formula % 1. Incident display 1986 Patent Application No. 405420, name of the invention Phytosensor, relationship with the case of the person making the amendment Patent applicant address No. 6-7-35, Kitashinyo, Tokyo Parts Store Name (2
18) Sony Corporation 4, Agent address: 1-35-1 Gotokuji, Setagaya-ku, Tokyo 1982
March 31, 2015 6, Drawing 7 subject to amendment, content of amendment The subdivision number r (C)J in Figure 2 is corrected to "[B]". There are no changes to the content of the drawing in Figure 2 or the subdivision number "(A)". 8. List of attached documents

Claims (1)

[Claims] (1) A first conductivity type semiconductor region and a second conductivity type semiconductor region which are arranged on an insulating substrate to be spaced apart from each other; and an electrode formed on a surface of the intrinsic semiconductor region opposite to the light incident side with an insulating layer interposed therebetween.