JPH0715586B2 - Photoconductor - Google Patents

Description

TECHNICAL FIELD The present invention is composed of an amorphous material containing silicon atoms and / or germanium atoms as main components and germanium carbide containing a group III atom of the periodic table. It relates to a photoconductor.

(Prior Art) Conventionally, amorphous hydrogenated silicon and amorphous hydrogenated silicon germanium have excellent photoconductivity and heat resistance, and are non-polluting, so that they have been applied to imaging devices and electrophotographic photoreceptors. Development research is active.

FIG. 5 is a sectional view of a conventional photoconductor. In the figure, an oxide such as alumina (hereinafter abbreviated as Al ₂ O ₃ ) or silicon oxide (hereinafter abbreviated as SiOx) is used as the electron blocking layer 32 that blocks injection of electrons into the photoconductive layer on the Al substrate 31. , Or an organic polymer such as polycarbonate, or silicon nitride (hereinafter abbreviated as SiNx) is formed, then a photoconductive layer 33 such as amorphous silicon or amorphous silicon germanium is formed, and sputtering is further formed thereon. The transparent electrode 34 is formed by the method.
(Reference: JP 56-24356 and JP Sho 57-58161) blocking layer of the electron (invention Problems to be Solved) conventional SiOx, Al ₂ O _3, SiNx or organic high When it is composed of molecules or the like, it forms a barrier against holes in the photoconductive layer, which causes a problem in reduction of operating voltage (reduction of afterimage and residual potential in imaging devices and electrophotographic photoreceptors).

The object of the present invention is to eliminate the conventional drawbacks, a film containing germanium carbide (hereinafter abbreviated as GeCx) containing a group III atom of the periodic table as a main component is used as a blocking layer, and low dark current and low operating voltage To provide a photoconductor that is realized and has no loss due to absorption and reflection of incident light.

(Means for Solving the Problems) A photoconductor of the present invention comprises a film containing amorphous silicon containing at least hydrogen atoms or halogen atoms as a main component, and amorphous silicon germanium on a conductive substrate. A first layer made of any one of a film containing a main component and a film containing amorphous germanium as a main component or a combination thereof is formed, and further, a third layer of the periodic table is formed on the first layer.
At least a second layer containing germanium carbide containing a group atom as a main component is formed.

The first layer contains any one of oxygen atoms, nitrogen atoms, and carbon atoms, or a combination thereof. Further, the first layer contains at least one kind of boron atom and phosphorus atom.

Further, the germanium carbide containing a Group III atom in the periodic table, which is the second layer, contains either one or both of an oxygen atom and a nitrogen atom. Further, silicon carbide, germanium nitride, silicon nitride, or silicon oxide is formed between the conductive substrate and the first layer. Furthermore, between the conductive substrate and the first layer,
One of amorphous silicon, amorphous silicon germanium, and amorphous germanium containing a phosphorus atom and at least a hydrogen atom or a halogen atom is formed.

(Function) GeCx exhibits n-type conduction, but when it contains a group III atom of the periodic table, it exhibits p-type conduction. Therefore, GeCx containing a Group III atom of the periodic table prevents injection of electrons from the outside into the amorphous silicon that is the photoconductive layer, and also acts as a barrier against holes in the amorphous silicon. Since it is not formed, the dark current decreases and the operating voltage decreases. Even when the photoconductive layer is made of amorphous silicon germanium or amorphous germanium having a narrow band gap, the band gap of GeCx is reduced by reducing the composition ratio x of GeCx carbon. Because it is easy to do
GeCx containing a group atom effectively acts as an electron blocking layer even for a photoconductive layer with a narrow band gap, and it is possible to obtain the same effect as when the photoconductive layer is amorphous silicon. . Furthermore, since an amorphous GeCx film having a large x becomes transparent to visible light and has a smaller refractive index than that of the photoconductive layer, when irradiating light from the GeCx layer side,
It is possible to significantly reduce the absorption loss and the reflection loss of the incident light. Further, when the photoconductor of the present invention is used as an electrophotographic photoreceptor, since amorphous GeCx has a large surface tension with respect to water, it is difficult for dew condensation even in a high humidity atmosphere, and image deletion and blurring can be suppressed.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 to 4.

GeH ₄ , Ge ₂ H ₆ , Ge
₃ H ₈ , GeF ₄ , GeHF ₃ , GeH ₂ F ₂ , GeH ₃ F, GeCl ₄ , GeHCl ₃ , GeH ₂ Cl ₂ , G
Source gas of Ge atoms such as eH ₃ Cl, GeF ₂ , GeCl ₂ and CH ₄ , C ₂
H _6, the _{C 3 H 8, C 4 H} 10, C 2 H 4, C 3 H 6, C 4 H 8, C 2 H 2, C 3 H 4, C 4 feed gas C atoms, such as H ₆ The plasma CVD method used and the reactive sputtering method in Ar, H ₂ , CH ₄ , C ₂ H ₄ , and C ₂ H ₂ with Ge or GeC as the target are used.

The Group III atom of the periodic table contained in GeCx is preferably boron (B), aluminum (Al), gallium (Ga), or indium (In), and B and Al are most suitable. To include these atoms in GeCx, B ₂ H ₆ , BF ₃ , BCl ₃ ,
BBr ₃ , (CH ₃ ) ₃ Al, (C ₂ H ₅ ) ₃ Al, (iC ₄ H ₉ ) ₃ Al, AlCl ₃ , (CH ₃ ) ₃ G
Plasma of a, (C ₂ H ₅ ) ₃ Ga, (CH ₃ ) ₃ In, (C ₂ H ₅ ) ₃ In, etc.
In the CVD method, the raw material gas of Ge atoms or the raw material gas of C atoms is mixed. Further, in the reactive sputtering method, the Ar, H ₂ , CH ₄ , C ₂ H ₄ , and C ₂ H ₂ may be mixed. Further, amorphous silicon of the photoconductive layer (hereinafter, depending on the type of atoms contained in the film, a-Si: H, a-Si: H: X, a-Si: X
(Abbreviated as X = halogen atom) is SiH ₄ , Si ₂ H ₆ , Si _{3
H 8, SiF 4, SiHF 3} , SiH 2 F 2, SiH 3 F, SiCl 4, SiHCl 3, SiH 2 Cl 2, Si
The source gas of Si atoms such as H ₃ Cl or these gases is
Plasma CVD method using gas diluted with r, He, H _2, etc.,
Alternatively, by using Si as a target, it can be formed by a reactive sputtering method or a vapor deposition method in a mixed gas of Ar and H ₂ or in a mixed gas of Ar and SiF ₄ . Amorphous germanium (Depending on the type of atoms contained in the film, a-Ge: H, a-Ge: H: X, a-Ge: X
(Abbreviated as X = halogen atom) is a plasma CVD method using the above-mentioned source gas of Ge atoms or a gas obtained by diluting these gases with Ar, He, H ₂ or the like, or an Ar targeting Ge. In a mixed gas of H ₂ or Ar and GeX ₄ or GeH
Formed by reactive sputtering or vapor deposition in a mixed gas of _4-n X ₄ (where X = F or Cl, n = 1,2,3), and amorphous silicon germanium (hereinafter contained in the film A-Si _1-x Ge _x : H, a-Si _1-x Ge _x : H: X or a-Si _1-x Ge _x :
X (abbreviated as X = halogen atom) similarly applies to the above G
A plasma CVD method using a mixed gas of a raw material gas of e atom and a raw material gas of Si atom or a gas obtained by diluting this mixed gas with a gas such as Ar, He, H ₂ , or a target or Si mixed with Si and Ge. Mixed gas of Ar and H ₂ or Ar and SiX ₄ or SiH _4-n X using two targets of Si and Ge
_n (where X = halogen atom, n = 1,2,3) and / or GeX ₄ or GeH _4-n X _n (where X = F or Cl, n = 1,
It is formed by reactive sputtering or vapor deposition in a mixed gas of 2,3).

Examples 1 to 3 describe examples using the plasma CVD method, and Example 4 describes examples using the reactive sputtering method.

Example 1 In FIG. 1, a glass substrate is a capacitively coupled plasma CV.
After arranging in the apparatus D and evacuating the reaction vessel to 5 × 10 ⁻⁶ Torr or less, the glass substrate on which the ITO transparent electrode 4 is formed is heated to 150 to 250 ° C. SiH ₄ : 100sccm, diluted with hydrogen 4
Introducing 0 ppm concentration of B ₂ H ₆ : 2 to 4 sccm into the reaction vessel,
After adjusting the pressure in the reaction vessel to 0.2 to 1.0 Torr,
Boron added with 3.56MHz high frequency power 150 to 400W i
A type a-Si: H layer 3 is formed on the ITO transparent electrode 4 to a thickness of 8 μm, and then G
eF ₄ : 1 to 5sccm, C ₂ H ₄ : 5 to 10sccm, 1% concentration of B ₂ H ₆ : 0.5 to 20sccm diluted with He was introduced, and boron was added at a pressure of 0.2 to 1.0 Torr and high frequency power of 50 to 200W. The formed GeCx layer 2 is laminated by 0.2 μm. Further, the Al electrode 1 is formed by the sputtering method or the vacuum evaporation method.

FIG. 2 shows the voltage dependence of the dark current and the photocurrent with respect to the light with a wavelength of 435 nm when a voltage is applied such that the upper Al electrode 1 is negative and the lower ITO transparent electrode 4 is positive. As a conventional example for comparison, as shown in FIG. 5, instead of the boron-doped GeCx layer 2 shown in FIG. 1, SiH was formed by a plasma CVD method.
₄ : 2 to 10 sccm, NH ₃ : 50 to 100 sccm, gas pressure 0.2
To 1.0 Torr and SiNx produced with a discharge power of 100 to 400W
FIG. 2 shows the voltage-current characteristics in the structure in which the layer 0.2 μm is used as the blocking layer 32. As is clear from the figure, the embodiment of the present invention has a low operating voltage and a low dark current.

SiNx layer (blocking layer) 32 is GeCx layer 2 with boron added
It acts as an electron blocking layer similarly to the above, but forms a barrier against holes in the boron-doped i-type a-Si: H layer 3 and does not form a barrier.
The operating voltage is higher than.

In addition, the photoconductor shown in FIG.
When the negative charge was used as a state where the electrode 1 and the external circuit were removed), the saturated surface potential was 500V and the residual potential was 5V or less. Embodiments of the present invention provide an electrophotographic photoreceptor having a large charge acceptance and a small residual potential. Further, instead of the a-Si: H layer 3 containing boron, a-Si _1-x Ge _x : H, a-Si _1-x Ge _x :
H: X, a-Si _1-x Ge _x : X (X = halogen atom) or a-Ge:
H, a-Ge: H: X, a-Ge: X (X = halogen atom) in a single layer of a film or a combination of a material having a large band gap and a material having a large band gap (for example, from the GeCx layer 2 side to a −Ge: H
And a-Si: H, a-Si _1-x Ge _x : H and a-Si: H or a-Ge: H and aS
An example is a combination of laminated i _1-x Ge _x : H. Further, even when the halogen atom X is contained, the same combination is possible, the boron-added GeCx layer 2 brings about the same effect as described above.

Example 2 In FIG. 3, the mirror-polished Al drum 10 was placed in a capacitively coupled plasma CVD apparatus, and the inside of the reaction vessel was 5 × 10 ⁻⁶ T.
After exhausting below orr, the Al drum 10 is 150 to 250 ℃
Heat to. SiH ₄ : 100 to 200sccm, hydrogen diluted 20p
PH _{3 in} pm concentration: 0.5 to 2 sccm, pressure: 0.2 to 1.0 Tor
r, phosphorus added under the conditions of high frequency power 150 to 400W a-
Form Si: H layer 13 of 10 to 15 μm, then GeF ₄ : 2 to 10
sccm, SiH ₄ : 100 to 200 sccm, hydrogen-diluted 40 ppm concentration B ₂ H ₆ : 2 to 4 sccm introduced, pressure 0.2 to 1.0 Torr,
Boron-doped a-Si _1-x Ge _x with high-frequency power of 150 to 400 W:
An H: F layer 12 having a thickness of 2 to 4 μm is formed, followed by GeH ₄ : 10 to 50 sccm and 1% B ₂ H ₆ : 50 to 100 sc diluted with He.
Then, a GeCx layer 11 having a boron content of 0.2 to 1 μm is formed at a pressure of 0.2 to 1.0 Torr and a high frequency power of 100 to 500 W. Further SiH ₄ : 50 to 100 sccm, CH ₄ : 20 to 80
sccm, pressure 0.2 to 1.0 Torr, high frequency power 150 to 300
A silicon carbide (hereinafter abbreviated as SiCx) layer 14 is formed by W to 1000 to 2000Å to obtain an electrophotographic photoreceptor.

The spectral sensitivity of this electrophotographic photosensitive member in negative charging is high in a wide range of 400 to 800 nm, and the boron-added a-Si _1-x Ge _x : H: F layer 12 is used as a photoconductive layer for long-wavelength light. By adding to the a-Si: H layer 13 with phosphorus added,
It was confirmed that the light sensitivity in the near infrared region was improved. This electrophotographic photosensitive member was mounted on a laser beam printer using a semiconductor laser with a wavelength of 800 nm as a light source, and clear printing could be confirmed.
In this case, the boron-doped GeCx layer 11 has a carbon composition ratio x
Is widened to widen the band gap, and not only acts as a blocking layer for electrons but also as a window layer that does not absorb light for exposure. Further, in order to stabilize the electrophotographic photosensitive member and increase its resistance, boron was added.
_{a-Si 1-x Ge x} : H: F layer 12 and, or phosphorus added the a-Si: H layer
Carbon atoms, oxygen atoms or nitrogen atoms may be added to 13, and in order to improve adhesion between the phosphorus-added a-Si: H layer 13 and the Al drum 10, oxygen atoms or nitrogen atoms and phosphorus atoms are added. A-Si: H layer 13 with added a-Si: H and phosphorus and Al drum
It may be formed between 10. Further, in this case, the SiCx layer 14 was used as the surface protection layer, but instead of SiCx, SiOx, SiN
x, GeNx or GeCx may be used. In addition, the photoconductive layer has a boron-doped a-Si _1-x Ge _x : H: F layer 12 and a phosphorus-doped a-Si: H layer.
Instead of 13, a-Ge: H with boron added and a-Si with phosphorus added
_{Even if a 1-x} Ge _x : H stack or a boron-added a-Ge: H and phosphorus-added a-Si: H stack is used,
Layer 11 effectively acts as an electron blocking layer.

Example 3 In the same manner as in Example 2, the plasma CVD method was performed to obtain 150 to 200
SiH ₄ : 100 to 200sccm on Al drum heated to ℃,
Hydrogen-diluted 100 ppm concentration PF ₃ : 100 to 200 sccm, gas pressure 0.2 to 1.0 Torr, high frequency power 100 to 400 W, and phosphorus-doped n-type a-Si: H: F film 0.2 to 1.0 μm formed, followed by SiH ₄ : 100 to 200 sccm, gas pressure 0.2 to 1.0 Tor
r, 10 to 20μ a-Si: H film with high frequency power 100 to 400W
m. Furthermore, GeH ₄ : 2 to 10 sccm, CH ₄ : 40 to 100 sccm, 10% BF ₃ : 0.5 to 20 sc diluted with He.
cm, gas pressure 0.2 to 1.0 Torr, high frequency power 100 to 4
Form GeCx layer 1000 to 5000Å with boron added at 00W,
An electrophotographic photoreceptor was produced. When this electrophotographic photosensitive member was mounted on a commercially available copying machine, it was confirmed that negative electrification gave a printing durability of 800,000 sheets or more and good images.

Example 4 In FIG. 4, a glass substrate 21 on the surface of which an ITO transparent electrode 20 was formed was placed in a magnetron sputtering apparatus, a Ge polycrystal was targeted at a substrate temperature of 250 ° C., and Ar: 1 to 3 mT.
Orr, CH ₄ : 2 to 6 mTorr, 13.56 MHz High frequency power of 300 to 500 W is used to form a GeCx layer 22 of 1000 to 3000 Å. next,
Targeting a polycrystal of Si, Ar: 1 to 10 mTorr, 20 ppm concentration of B ₂ H ₆ diluted with hydrogen: 0.3 to 0.4 mTorr, and a-Si: H layer 23 with boron added at high frequency power of 300 to 800 W.
To 3 μm. Then, 10% concentration B ₂ H ₆ : 1 to 3 mTorr, CH ₄ :, which was diluted with Ar by targeting Ge polycrystal.
A GeCx layer 24 having a boron content of 2 to 6 mTorr and a high frequency power of 300 to 500 W is formed at 1000 to 3000 Å. Further, an electron beam landing Sb ₂ S ₃ layer 25 is deposited by 1000 Å to manufacture an image pickup tube target. Since the ITO transparent electrode 20 is positively biased with respect to the cathode 26, electron-hole pairs generated by incident light from the glass substrate 21 side are separated by the electric field in the film. The holes drift to the upper surface in the boron-doped a-Si: H23 layer, and the electrons gather on the lower ITO transparent electrode 20. In the GeCx layer 24 added with boron, holes easily travel,
The GeCx layer 22 functions as an electron blocking layer, and electrons easily travel therethrough, and functions as a hole blocking layer. Further, the holes in the a-Si: H layer 23 became easy to move by the addition of boron, and in the embodiment of the present invention shown in FIG. 4, the operating voltage was low, and good characteristics such as little baking and afterimage were obtained. .

Further, instead of the GeCx layer 22, SiNx, GeNx, SiOx, SiCx can be used to obtain the same result as above.

(Effect of the Invention) The photoconductor according to the present invention has a low dark current and a low operating voltage and can be used as an electrophotographic photoreceptor, an imaging device or a photodiode. In particular, when light is irradiated from the a-GeCx side, by using an a-GeCx film containing a high amount of carbon, there is no reflection loss or absorption loss of incident light and high photosensitivity is obtained. Further, when used as an electrophotographic photoreceptor, image deletion and blurring can be suppressed even in a high-humidity atmosphere, so that the element structure is effective for actual use. Further, GeCx has a large surface hardness, and by increasing x, it becomes transparent to visible light. Therefore, it is suitable for the surface protective layer of the photoconductor and has various practical effects.

[Brief description of drawings]

FIG. 1 is a sectional view of a photoconductor in one embodiment of the present invention,
2 is a diagram showing the voltage dependence of dark current and photocurrent, FIG. 3 is a sectional view of an application example of the photoconductor of the present invention to an electrophotographic photoreceptor, and FIG. 4 is a photoconductor of the present invention. FIG. 5 is a cross-sectional view of an example of application to the image pickup tube target, and FIG. 5 is a cross-sectional view of a conventional photoconductor. 1 ... Al electrode, 2,11,22,24 ... GeCx layer, 3 ... i-type aS
i: H layer, 4,20 ... ITO transparent electrode, 10 ... Al substrate drum, 12
_{...... a-Si 1-x Ge} x: H: F layer, 13,23 ...... a-Si: H layer, 14 ...... SiC
x layer, 21 …… glass substrate, 25 …… Sb ₂ S ₃ layer, 26 …… cathode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-63960 (JP, A) JP-A-61-198622 (JP, A) JP-A-56-121041 (JP, A) JP-A-61- 94049 (JP, A)

Claims (6)

[Claims] 1. A film containing amorphous silicon containing at least a hydrogen atom or a halogen atom as a main component, a film containing amorphous silicon germanium as a main component, and an amorphous germanium film on a conductive substrate. A first layer made of any one of the constituent films or a combination thereof is formed, and the main component is germanium carbide containing an atom of Group III of the periodic table on the first layer. A photoconductor comprising at least a second layer. 2. The light according to claim 1, wherein the first layer contains any one of an oxygen atom, a nitrogen atom, a carbon atom or a combination thereof. conductor. 3. The photoconductor according to claim 1, wherein the first layer contains at least one kind of boron atom and phosphorus atom. 4. The germanium carbide containing a Group III atom of the periodic table, which is the second layer, contains either one or both of an oxygen atom and a nitrogen atom. 4.) The photoconductor according to any one of items (3) to (3). 5. A silicon carbide, a germanium nitride, a silicon nitride, or a silicon oxide is formed between the conductive substrate and the first layer. The claims (1) to (4). The photoconductor according to any one of items. 6. Amorphous silicon, amorphous silicon germanium, and amorphous germanium containing a phosphorus atom and at least a hydrogen atom or a halogen atom between the conductive substrate and the first layer. The photoconductor according to any one of claims (1) to (4), wherein any one of them is formed.