JPS60109273A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the resolution by a method wherein a one-dimensional photosensor element is formed into a P/I/N sandwich structure by using amorphous Si carbide films, the thicknesses of which films are then made specific. CONSTITUTION:An ITO is formed on a transparent glass substrate 1 and made as a clear common electrode. After an N type amorphous Si carbide film 3 about 0.5mum-1mum thick is formed thereon, an I type amorphous Si carbide film 4 is formed and made as a photosensitive layer, and a P type amorphous Si carbide film 5 and a discrete electrode 6 of aluminum or the like are successively formed thereon. In the case of the incidence of white fluorescent light from the glass substrate side, the wavelength regions of lights reaching the film 4 are cut more in the surface layer in lights having shorter wavelengths, having the same effect as in the case of interposing color filters. Therefore, the S/N ratio can be set large, and the resolution can be improved by controlling the thickness of the filter layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Even when using a light source with a large spectral radiant flux, for example, a white photovoltaic light source, the present invention can achieve photoelectric conversion equivalent to that when using a green light source without using a color filter. The present invention relates to a photoelectric conversion device that is capable of performing a distributed refractive index fiber lens array and also preventing deterioration in resolution due to chromatic aberration caused by a distributed index fiber lens array.

Recently, a technology called a close-contact optical sensor has been developed as a photoelectric conversion device for facsimile machines, which has the same reading width as the original, and can be used in close contact with the original, making the distance between the original and the optical sensor element much smaller. It is attracting attention. In this contact type image sensor driving method, B@
There is a so-called storage type that uses a photodiode formed of a thin film of an amorphous semiconductor such as As-Te or amorphous silicon. Among them, those using amorphous silicon are easy to form over large areas.
It has features such as being heat resistant, highly reliable, and a non-polluting material. As an accumulation type photosensor element structure, there is one using an amorphous silicon film having a P/1/n sandwich structure having a blocking electrode. Figure 1 1
c shows a cross-sectional structure of a photosensor element with a P/i/n-type switch structure.

At this time, the thickness of the P-type or N-type amorphous silicon film as the carrier blocking electrode layer is 0.05
Since a value on the order of μm or less is sufficient, the above-mentioned value is usually selected. For example, light passing through a transparent electrode 2 made of ITO (indium tin oxide) formed on a glass substrate 1 and an n-type 7 mol 7 as silicon film 3 of, for example, about 0.005 μm is used as a photosensitive portion.
Electrons generated in the amorphous silicon film 4 are blocked by the P-type amorphous silicon film 5 of about 0.05 μm, and holes are blocked by the N-type amorphous silicon film 3, for example.

By the way, as an example of a contact type image sensor, as shown in FIG.
0 (hereinafter referred to as a lens array), there is a method of forming a same-magnification image on the photosensor element array 40 and reading it. Usually light source 2
A monochromatic light source 20 with a color filter provided on a white fluorescent light source (LID) or a white fluorescent light source is used to prevent deterioration of the optical resolution due to chromatic aberration of the lens array 300. However, L.E.
Since the spectral radiant flux of D-light offshore is small, reading at high speeds using the storage edge has the drawback of insufficient light intensity and deterioration of the signal-to-noise ratio.

Further, when a white fluorescent photoelectric light source is used as a light source, there is a problem of deterioration of resolution as described below. For example, if the black stripe image 200 is the shaded area in the wavelength range that is imaged at 1× as shown in FIG. The output is, for example, 1, and on the contrary, no light enters the entire area on the optical multiplexer element 101, and the optical signal output is, for example, 0.

However, outside the wavelength region where the image is formed at the same magnification, the image is no longer the same size due to chromatic aberration. For example, in the short wavelength region, the black stripe image 200 becomes an enlarged image 300 surrounded by a single point MIN in the figure, for example. In the long wavelength region, the image is a reduced image 400 surrounded by a two-dot chain line in the figure. Therefore, when the photosensor element has spectral sensitivity in the above wavelength range, the optical signal output of the photosensor element 100 is, for example, 0 in the short wavelength range.
．． On the contrary, in the long wavelength region, the black signal output of the optical sensor element 101 decreases to about 0.15 [1
[,L, In the end, resolution deteriorates no matter which K is used.

For example, since the i-type amorphous silicon film has a spectral sensitivity as shown in FIG.
It becomes a degree.

Furthermore, when an amorphous silicon film is used, its absorption edge is from 700 nm to 800 nm, which is in the range from red light to near-infrared light, so that an image caused by red light cannot be converted into light ηL. Normally, the document read by the facsimile machine Fj is black on a white background, but it is also necessary to read the red color caused by the ink of a seal or the like. However, in the photoelectric conversion of an image using red light using the amorphous silicon film described above, red characters and lines cannot be read.

The object of the present invention is to provide a photoelectric conversion device that uses a white fluorescent photoelectric light source with a large spectral radiant flux, does not require any additional color filters, and has less deterioration in resolution equivalent to that using a normal green light source. Our goal is to provide the following.

According to the present invention, a light source for illuminating a document and a distributed refractive index rod lens 7 ray for forming an image of the light reflected from the surface of the document, and the lightness of the image formed by the distributed refractive index rod lens 7 ray are provided. In a photoelectric conversion device comprising at least a one-dimensional photosensor element that performs photoelectric conversion, the one-dimensional photosensor element is formed in a P/i/n sandwich structure using an amorphous silicon carbide film, and the distribution The refractive index rod lens 7 ray is attached to the pyi! on the side that becomes the imaging surface. Or an n-type amorphous silicon carbide film with a film thickness of 0.5 μm to 1 μm.
A photoelectric conversion device is obtained.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

- First, a transparent common electrode is formed by sputtering, for example, ITO on a glass substrate, and then ξ, for example, P
H3/SiH4+CH4: 0.2%, C/Si=l
By glow discharge method in an atmosphere of about O-15,
An n-type amorphous silicon carbide film having a thickness of about 0.5 μrn to 1 μm is formed. Then, an n-type amorphous silicon carbide film not doped with impurities is formed to a thickness of about 2 μm to form a photosensitive layer.

On this, a P-type amorphous silicon carbide film of K, for example, BH/5in4+CH4=60.2% and C/thickness=10 to 15%, and individual electrodes of aluminum or gold, for example, are sequentially formed thereon. This P-type amorphous silicon carbide film does not have to be as thick as the Kn-type film (it only needs to have a density of about 0.05 μm and serve as a blocking contact for electrons).

In the optical sensor element of this configuration, when white light is incident from the glass substrate side, it passes through the n-type 7M 7A silicon carbide film and generates light from the n-type amorphous silicon carbide that is the photosensitive layer. As shown in Figure 5, the wavelength range of the light that reaches the film is shorter as it is cut by the surface layer, so it has the same effect as a color filter. When the thickness of the amorphous silicon carbide film is 0.5 μm or more, it acts as a filter with a gradient near the absorption edge. Especially in the example in the same figure, 5
There is an absorption edge near 50 nm. As the film thickness is further increased, the slope becomes steeper. Due to this characteristic and the spectral sensitivity characteristics of the n-type 7 mole 7 as silicon carbide film, the so-called sensitive wavelength region has the same effect as passing through a filter.

Therefore, as described above, images in the filtered wavelength range are not photoelectrically converted by the amorphous silicon carbide film of iMl, so deterioration in resolution can be suppressed.

In addition, as shown in Figure 5, the thicker the n-type amorphous silimanker film, which acts as a filter layer, the steeper the slope, which improves the resolution, but reduces the spectral sensitivity and increases the optical signal. Output becomes smaller.

Therefore, by controlling the film i of the filter layer, if you want to increase the signal-to-noise ratio, you can make the film thinner even if the resolution is slightly better, or if you want to improve the resolution, you can do the opposite. It is also possible to easily meet various uses such as.

In the case of the above-mentioned 4'liK main pod embodiment, the ratio of silicon to carbide is selected so that the absorption edge of the n-type amorphous silicon carbide film has a green light pressure around 550 nm. Therefore, it is possible to read red characters, lines, etc. on the surface of a document, and it can be fully used as a photoelectric conversion device for a normal facsimile machine. Note that it is not limited to green light in particular, but by appropriately selecting the ratio of silicon and carbide mentioned above, it is also possible to select light of a specific wavelength over the entire visible light range from about 4000 to 7000X. Become.

In the above example, n R'! Although the structure is such that the 7 mol 7 ascarbide film also serves as a filter, the structure is not limited to this, and the same effect can of course be obtained with a structure in which PM and n-type are reversed.

As explained above, according to the present invention, by using white fluorescent light with a large spectral radiant flux, the signal-to-noise ratio can be increased, and the optical sensor element can be used as 'CP / + /
By using a 7 mol 7 as silicon carbide film with an n-sandwich structure, it is possible to read red letters and lines compared to an amorphous silicon film, and an n-type or p-type amorphous silicon carbide film is used on the light incident side. The blocking layer has a thickness of 0.54 m to 1 μm and functions as a filter layer, which reduces deterioration in resolution per resolution.Moreover, since the blocking layer also serves as a filter layer, there is no need for extra processes. You can get the same effect.

[Brief explanation of drawings]

FIG. 1 shows an example of a cross-sectional view of an amorphous silicon carbide sensor element having a P/i/n type sandwich structure, in which 1 is a glass substrate, 2 is a transparent electrode, and 3.
4.5 are nW, iW, and P-type amorphous silicon carbide films, and 6 is an individual electrode. FIG. 2 shows an example of the configuration of a photoelectric conversion device.
2 is a document, 20 is a fluorescent photoelectric device, 30 is a distributed refractive index Radlens Frei, and 40 is a photosensor element 1. 3rd C is a diagram for explaining resolution deterioration due to chromatic aberration, where 100 is an optical sensor element, 200 is an image of a black stripe at the same-magnification imaging wavelength, and 300°400 is an image outside the same-magnification imaging wavelength. It is a statue with dotted stripes. FIG. 4 shows the spectral sensitivity characteristics of a type 1 amorphous silicon film and the filter effect of an n-type or p-type amorphous silicon film. FIG. 5 shows the spectral sensitivity characteristics of an l-type amorphous silicon carbide film and the filter effect of an n-type or p-type amorphous silicon carbide film, which is an embodiment of the present invention. 1st [8 Fig. 2 0 Fig. 3 Fig. 4 Fig. 5 i=lθ~tSz ;! OQ 4θθ 6θθ −θθθ

Claims (1)

[Claims] A light source for illuminating a document, a distributed index rod lens array for forming an image of light reflected from the surface of the document, and a one-dimensional photosensor element that performs photoelectric conversion according to the brightness of the image formed by the distributed index rod lens array. In a photoelectric conversion device composed of a small number of
/ n sandwich structure, and the Pm or ni amorphous silicon carbide film on the side that becomes the imaging surface of the distributed index rod lens array has a film thickness of 0.5 μm to 1 μm. Photoelectric conversion device.