JPH0462580B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor photoreceptor for a copying machine that has improved long wavelength sensitivity.

The present invention aims to improve the wavelength sensitivity of conventional electrostatic copying machine drums that use only amorphous silicon semiconductors, and to create a photoreceptor for electrostatic copying machines that is sufficiently sensitive to long wavelength light, especially near-infrared light. There is.

Conventionally, in drums using amorphous silicon, the wavelength sensitivity is the same as the visibility, so
Sensitivity to long wavelength light of 600 nm or more was virtually impossible. For this reason, if amorphous semiconductors are to be applied to laser printers that use such long wavelength light, particularly laser light, other structures are required.

That is, a typical example of the prior art is, for example, JARECT
Vol.Amorphous Semiconductor Technologies
&Devices (1983), OHMSHA edition pp325-337 especially
Shown in Figs 7.4.17-7.4.18. That is, a P-type semiconductor with a thickness of 0.5 μ on an aluminum substrate, a substantially intrinsic amorphous silicon (2.5 μ thick) doped with 10 PPM of boron, and a layer having a low energy band width on top of that. It is made of amorphous Si _1-x Gex (thickness 1.5μ), and on top of that is an amorphous silicon semiconductor (thickness 1.0μ).

However, amorphous Si _1-x Gex has some essential drawbacks as a semiconductor material.

The typical drawbacks are that germanium is a rare and expensive material, the starting materials GeH ₄ and GeF ₄ are difficult to create, and amorphous semiconductors have a wider energy band width than single crystal semiconductors, but this amorphous structure cannot be used. We are trying to create a layer with a low energy band width by using this method. and so on.

For these reasons, even though it was expected to be excellent for laser printing, it was virtually impossible to put it into practical use.

The present invention has been made in order to eliminate these drawbacks, and instead of making the second layer having a lower energy band width on the amorphous semiconductor layer on the substrate side have the same crystal structure, it is made to have a more crystalline structure. The layer is made of a material with a high degree of crystallization, such as a polycrystalline silicon layer. As a result, the second layer sensitive to long wavelength light is
The optical energy band width can be 1.2 to 1.5 eV, typically 1.3 eV.

The manufacturing method is to deposit the first layer with plasma.
Si, Si ₃ N _4-x (0<X<4), SiC _1-x (0
<X<1) or SiO _2-x (0<X<2), the second layer is formed by reducing or removing these C, N, and O additives. do. Thereafter, this second layer is photo-annealed by intense light irradiation to polycrystallize this layer. Then, most of the hydrogen and halogen elements in this layer are degassed, and the optical Eg becomes 1.6 to 1.5 eV when the temperature of the irradiated surface is low (600 to 700 degrees Celsius) due to photoannealing, and 700 to 700 degrees Celsius.
1.5-1.4eV at ~00℃ and 1.4-1.4eV at 800-900℃
1.2eV each.

At this time, since the inner first layer contains more additives such as oxygen, polycrystalization is inhibited.

Furthermore, in the present invention, a third layer is again formed on these upper surfaces by plasma CVD using a substantially intrinsic amorphous semiconductor or semi-insulator, similar to the second layer.

Examples thereof will be described below with reference to the drawings.

FIG. 1 shows the elements of an electrostatic copying machine to which the present invention is applied. That is, in FIG. 1A, a first layer 20 having a PI junction or an NI junction on a conductive substrate, a polycrystalline semiconductor layer (second layer) 17 having a low energy band width, and a blocking layer (third layer) on the surface. A photoconductive semiconductor 1 consisting of a layer) 21 is provided. Furthermore, after this, the entire area is charged with, for example, a positive charge (FIG. 1B), and as shown in FIG.
6". Then, the static electricity in this area is released to the conductor 2. In addition, among the electricity/hole pairs generated by photoexcitation, negative electrons in the figure recombine with this positive static electricity and neutralize it. In this way, it was possible to selectively distribute static electricity on the semiconductor.

FIG. 2 shows the principle of an electronic copying machine that applies this principle and is provided with a photoconductive semiconductor layer using a semiconductor formed into a rotating drum.

That is, the surface portion of the rotating drum is provided with a multilayer structure of a P or N type semiconductor (in the drawing, a P type semiconductor layer) and an intrinsic or substantially intrinsic semiconductor, as in FIG.

Further, the static electricity emitted from the static electricity generation source 8 is uniformly distributed on the blocking layer on the upper surface of the drum as shown in FIG. Further, reflected light 5 from an object (for example, the surface of a printed paper) 11 from a light source 7 passes through a slit 9 and is irradiated onto the drum. Then, a photovoltaic force is generated in the semiconductor in the irradiated surface area, and the recombination of the negative charges and the release of the positive charges to the substrate conductor produce a density of static electricity 4 according to the reflected light 5.

Further, black powder of carbon powder or a mixture similar thereto (particle size of 1.0 to 100 microns) is distributed on the surface of the rotating drum in 12 areas.
This powder then adheres to the drum surface in proportion to the amount of static electricity. Perform so-called "visualization".

Furthermore, the rotation of this drum (speed is 1 to 10
An object to be copied, for example, a new piece of paper 13, is moved in contact with the surface of this black powder at the same speed as (seconds/rotation),
This powder is adhered onto the object to be copied. Thereafter, this paper 13 undergoes printing and fixing to complete the copy. After the powder remaining on the surface of the drum is completely removed by the brush 14, it reaches the first source of static electricity generation.

FIG. 3 shows a vertical joint view of the photoreceptor for an electrostatic copying machine according to the present invention.

In the drawing, the surface of a conductor substrate or drum 2 is provided with a layer 20 having a first intrinsic or substantially intrinsic conductivity type. This layer includes a layer 15 of P or N type semiconductor and a layer 1 of intrinsic or substantially intrinsic type.
6 and more. For example, layer 15 is made of P-type amorphous silicon, and layer 16 is made of a semiconductor or semi-insulator of amorphous silicon doped with about 10 PPM of boron and 1 to 10 atomic percent of oxygen, carbon, or nitrogen.

Furthermore, a semiconductor layer having a higher crystallinity than this first layer is provided thereon. This layer has a smaller energy band width than the first layer, and is preferably the first layer.
It consists of the same main component material as the layer.

This second layer 17 is made of polycrystalline silicon doped with boron, and is further made of an amorphous semiconductor or semi-insulator made of the same material as layer 16 as a blocking layer thereon.

As a result, layers 15, 16, 21 have an optical energy band width of 1.7 to 1.8 eV, and layer 17
has 1.4-1.5eV.

FIG. 3B shows an energy band diagram corresponding to FIG. 4B. The third layer on the surface consists of a semiconductor 18 and an insulator 19.

The manufacturing method will be abbreviated.

By adding 0.5% by volume of diborane to silane using a known plasma CVD method, a P-type amorphous semiconductor 15 was formed to a thickness of 0.5μ at a temperature of 250°C and a pressure of 0.4torr.
was formed on an aluminum substrate. Furthermore, silane with B ₂ H ₆ /SiH ₄ = 10 PPM and nitrogen peroxide with N ₂ O / SiH ₄ = 2% by volume were introduced onto this upper surface.
SixO _2-x to a thickness of 2.5μ using the same plasma CVD method
(0<X<2) is formed.

After that, the entire body is thoroughly evacuated to remove nitrogen peroxide from the mixture, and a substantially intrinsic amorphous semiconductor is processed to 0.5 μm using the same plasma CVD method.
(semiconductor material for the second layer). Further, this surface is irradiated with strong light, such as laser light, to polycrystallize the amorphous silicon layer to a predetermined surface temperature of 700 to 1000°C. At this time, the inner layers 15 and 16 were prevented from being heated to prevent hydrogen or halogen elements from being degassed from the inner first layer.

A xenon lamp may be used for this strong light annealing. In the present invention, an excimer laser (XeCl) was used. It is effective to carry out the polycrystallization step by simultaneously performing the polycrystalization step while forming the silicon layer by applying pulsed light irradiation (pulse width of about 50 ns is repeated several times). At this time, the temperature of the irradiated part was 700 to 1000°C (the degree of crystallinity varies from about 2 to 9%), and for example, about 50% crystallization was achieved at 800°C.

Furthermore, after these steps, N ₂ O was again added using the silane plasma CVD method similar to the formation of the layer 16 to form the third layer 21 to a thickness of 0.5 μm.

In the manner described above, a photoreceptor having the vertical cross-sectional view shown in FIG. 3 was produced.

FIG. 4 shows four examples within the energy bands of the present invention.

FIG. 4A is particularly shown in the manufacture of FIG. For example, 2.5μ), polycrystalline silicon semiconductor 17 forming a well-type potential.
(thickness e.g. 0.5μ), and a substantially intrinsic semiconductor or semi-insulator (thickness
1.0μ).

In FIG. 4B, when performing polycrystallization, a xenon lamp was used instead of a laser beam, and a continuous band transition 23 was made inside. Furthermore, a silicon nitride insulating film 19 was provided on the surface as a blocking layer.

In FIG. 4C, a semi-insulator 15 is made of Si ₃ N _4-x (0<
X<4) For example, by setting X=3, both positive and negative images can be constructed.

In FIG. 4D, only an insulating film is provided as the third layer on the upper surface of the polycrystalline semiconductor 17 as a blocking layer.

In the above explanation, the semi-insulating film is N ₂ O
into plasma by mixing silane (SinH _2o+2 n≧1)
Formed by CVD method. However _{, even if} SixC _{1 - x ( 0 <} Si ₃ N _4-x (0<X<
4). Further, in order to promote the drift of holes toward the substrate conductor, the optical energy band width of the layer 16 may be made W-N (wide-to-narrow) from the surface side to the inside side. Further, the addition of boron may be gradually increased from the surface side toward the inner side.

In the present invention, FIGS. 3 and 4 are A, B,
D mainly shows the case where the surface is charged with positive static electricity. However, the first layer may be an I-N junction instead of an I-P junction, and a method of charging the first layer with electricity may be used. Further, as shown in FIG. 4C, polarity may be used.

By adopting the configuration shown above, conventionally known amorphous semiconductors alone can
Only the wavelength region of 700nm was covered. Also, even if you don't use germanium, 600 ~
Sufficient spectral sensitivity was achieved in the wavelength range of 900 nm.

In terms of cost, we were able to achieve exactly the same characteristics without using the extremely expensive material Germane. In this case −
It is safe because it does not use polluting materials such as CdS.

Furthermore, in the present invention, germanium may of course be added to the structure shown in FIG. 4 instead of using only silicon. However, in that case, price increases cannot be avoided.

Further, an organic resin may be coated on the upper surface of the energy band diagram in FIG. 4 as part or all of the third layer to reduce the price of the photoreceptor.

[Brief explanation of the drawing]

FIG. 1 shows the principle of local charging in the copying machine of the present invention. FIG. 2 shows the principle of a drum type electrostatic copying machine. FIG. 3 shows a longitudinal sectional view of the photoreceptor of the present invention. FIG. 4 shows an energy band diagram of the photoreceptor of the present invention.

Claims (1)

[Scope of Claims] 1. A first layer of a non-monocrystalline semiconductor or semi-insulator having photoconductivity on a substrate or drum having a conductive surface; a second layer having a small energy band width, and a third layer having an energy band width equal to or greater than that of the first layer stacked thereon,
A copying machine characterized in that the second layer is made of a semiconductor or a semi-insulator having a higher degree of crystallinity than the first or third layer. 2. In claim 1, the first layer comprises a P- or N-type semiconductor or a semi-insulator with higher insulating properties and the semiconductor or semi-insulator in close contact on a substrate or drum having a conductive surface. 1. A copying machine comprising a non-single crystal semiconductor or semi-insulator to which intrinsic or substantially intrinsic hydrogen or halogen elements are added. 3 In claim 1, the first layer is
Si, Si ₃ N _3-x (0<X<4), SiC _1-x (0<X<1)
Or it becomes a semiconductor or semi-insulator with an amorphous structure of SiO _2-x (0<X<2), and the second layer is Si, Si ₃ N _4-x (0<X<4), SiC _{1- x} (0<X<
1) A copying machine characterized by containing SiO _2-x (0<X<2) as a main component.