JPS61290778A - Photoelectric conversion element - Google Patents

Abstract

PURPOSE:To reduce leakage currents, and to improve a signal/noise ratio by coating a stepped section in the surface of an amorphous semiconductor layer with an insulating layer and forming an electrode to a light-receiving section for the amorphous semiconductor layer. CONSTITUTION:A plurality of first electrodes 2 consisting of chromium thin-films are shaped on a straight line on a glass substrate 1. A hydride amorphous silicon film 3 is formed onto the first electrodes 2. Windows are bored only by the same width as the first electrodes 2 as light-receiving sections, and polyimide 4 is shaped as insulating layers. A tin oxide film is formed to a light- receiving section for the amorphous silicon film 3, and used as a second electrode 5. According to such constitution, field concentration at stepped sections in the amorphous silicon film 3 is reduced, thus minimizing leakage currents.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photoelectric conversion element used, for example, in a document reading device such as a facsimile, and particularly relates to a photoelectric conversion element using an amorphous semiconductor as a photoelectric conversion material.

[Prior Art] FIG. 2 is a cross-sectional view of a photoelectric conversion element using a conventional amorphous semiconductor integrated as a charge conversion material, disclosed in Japanese Patent Laid-Open No. 58-84457. In the figure, (1) is the substrate,
(2) is a plurality of eleventh elements formed in parallel on the substrate (1).
an amorphous semiconductor layer formed to cover the first electrode, for example, the lower one electrode, (3) the IdF section electrode;
) is a second electrode formed on the amorphous semiconductor layer (3), for example, an upper transparent electrode.

Next, the operation will be explained. When the upper transparent electrode (5) and the amorphous semiconductor layer (3) are brought into contact, a Schottky barrier is formed due to the interaction of work R and loss.

As a result, a contact potential appears between the upper transparent electrode (5) and the amorphous semiconductor layer (3), resulting in rectification.

When a voltage is applied to the device shown in FIG. 2 so that the upper transparent electrode (52 side) is negative and the lower electrode (2) side is positive, the device becomes a reverse bias state.In this reverse bias state, the upper When light is incident from the transparent electrode (5) side, the light is absorbed by the amorphous semiconductor layer (3), generating electron-hole pairs and generating a photocurrent.
The element shown in the figure operates as a photoelectric conversion element.

[The shortcomings that the invention attempts to solve]

In the conventional photoelectric conversion element as described above, especially when used as a photosensor, it operates under a reverse bias pattern, so it is necessary to suppress leakage current. However, the second
In the photoelectric conversion element as shown in the figure, a common amorphous semiconductor layer (3) covers a plurality of F part electrodes (2) connected in a straight line on a substrate (1) in a band shape. ) is curved at the stepped portion at the end of the lower electrode (2). This amorphous semiconductor! The electric field concentrates at the step part in (3),
There was a problem that leakage current increased.

The present invention was made to solve the above-mentioned problems, and an object thereof is to obtain a photoelectric conversion element with very small leakage current and high S/N ratio.

[Means for solving problems]

The photoelectric conversion element in this invention includes a plurality of eleventh electrodes formed in parallel on a substrate, the first
@ Amorphous semiconductor layers formed in succession on each of the boxes, leaving a light-receiving part facing each of the first electrodes of this amorphous semiconductor layer, and a step on the surface of the amorphous semiconductor layer caused by the influence of the first electrodes. an insulating layer covering the portion, and a second electrode (1) formed on the light-receiving portion of the amorphous semiconductor layer.

[Effect]

The insulating layer in the present invention covers the stepped portion of the amorphous semiconductor layer and prevents the upper transparent electrode from being formed on the stepped portion of the amorphous semiconductor layer.

Therefore, it is possible to prevent the electric field from concentrating in this portion, and to significantly reduce the leakage current of the photoelectric conversion element.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a sectional view showing one embodiment of a photoelectric conversion element according to the present invention. (1) is a substrate, for example, a glass substrate, and on this substrate (1), as the 111th pole (2), for example, a chromium thin film (hereinafter referred to as thin film) with a film thickness of 0.1 to 0.3 μm is placed on a straight line. Form multiple pieces. On top of that, the film thickness is 0.62.
A plurality of μm thick hydrogenated amorphous silicon films (3) are successively formed to cover the first electric container (2) in a strip shape to form an amorphous semiconductor layer.

Next, for example, a window is opened in the same area as the first i-electrode (2) as a light receiving part, and a polyimide (4) having a thickness of about 111 m, for example, is formed as an insulating layer. Further, on the light receiving part of the amorphous silicon film (3), a t-film of, for example, indium tin oxide (hereinafter referred to as TO film) with a film thickness of about 0.2 μm is formed,
This is the second electrode (5).

The operation of the photoelectric conversion element according to the present invention will be explained.

In FIG. 1g1, a Schottky barrier is formed between the silicon film (5) and the amorphous silicon film (3).

When a voltage is applied so that the voltage is negative on the TO film electrode (5) side and positive on the α thin film electrode (2) side, the photoelectric conversion element shown in FIG. 1 becomes in a reverse bias state. Since a common amorphous silicon film (3) covers a plurality of linearly connected Cr thin film electrodes (2) in a band shape, the amorphous silicon film (3) is covered with the Cr thin film electrode (3) due to the influence of the thin film electrode (2). The amorphous silicon film (3) is curved on the edge of the amorphous silicon film (3) to form a step portion.This step portion of the amorphous silicon film (3) is insulated from the TO film electrode (5) by the polyimide (4)K.

There is little electric field concentration at the stepped portion of the amorphous silicon film (3), and therefore the leakage current is very small. When light enters this element from the TO film electrode (5) side, the light is absorbed by the amorphous silicon film (3) and electrons are
A hole pair is generated and a photocurrent is generated. In this way, the photoelectric conversion element shown in FIG. 1 has a very small leakage current, and the S/
It operates as a photoelectric conversion element with a high N ratio.

In the above embodiment, polyimide was used as the insulating layer (4), but other organic insulators and inorganic insulators such as silicon oxide and silicon nitride may be used. In addition, the second electrode (5
), but soot oxide, oxidizing indium indicum, etc. may also be used. Furthermore, although chromium was used as the first electrode (2), similar results can be obtained using titanium, aluminum, nickel, gold, platinum, or a multilayer stack of these. In the above embodiment, the width of the window of the amorphous semiconductor layer (3) required for light reception was set to be the same as the width of the first electrode (2).
It may be smaller than the width of 2). Furthermore, in the above embodiment,
Regarding the single layer of hydrogenated amorphous silicon as the amorphous semiconductor layer (3), we will mention hydrogenated amorphous silicon doped to P-type (Cplfl), hydrogenated amorphous silicon doped to 7-doped (1 layer), and hydrogen doped to n-type. A three-layer structure of amorphous silicon (n layer) may be used, or a two-layer structure of one layer/n layer and p layer/one layer may be used. Similar results can also be obtained by doping a trace amount of boron or arsenic into one layer. Further, instead of hydrogenated amorphous silicon, an amorphous semiconductor such as carbonized amorphous silicon, amorphous silicon darmanicum, etc. may be used.

[Effects of the Invention] As described above, according to the present invention, the plurality of first electrodes formed in parallel on the substrate, the eleventh
An amorphous semiconductor layer formed continuously on each of the electrodes, and a step on the surface of the amorphous semiconductor layer caused by the influence of the first electrode, leaving a light receiving part facing each of the first electrodes of this amorphous semi-quadruple layer. By providing an insulating layer covering the portion and a second electrode formed on the light receiving portion of the amorphous semiconductor layer, a photoelectric conversion element with very small leakage current and high S/N ratio can be obtained.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing a photoelectric conversion element according to an example of the present invention, and the wJz diagram is a conventional photoelectric conversion element. FIG. (1)... Board, (2)... First electrical box, (3)...
・Amorphous semiconductor layer, (4)...insulating layer, (5)
...Second electrode. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A plurality of first electrodes formed in parallel on a substrate, an amorphous semiconductor layer formed in succession on each of the first electrodes, and a light receiving portion facing each of the first electrodes of the amorphous semiconductor layer. and an insulating layer covering a stepped portion on the surface of the amorphous semiconductor layer caused by the influence of the first electrode, and a second electrode formed on the light receiving portion of the amorphous semiconductor layer.