Electrophotographic member with alpha-si layers

Abstract

In an electrophotographic member employing an amorphous silicon photoconductive layer, a part which is at least 10 nm thick inwardly of the amorphous silicon layer from the surface (or interface) of the amorphous silicon layer is made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 10 10 Ω.cm. The electrophotographic member exhibits a satisfactory resolution and good dark-decay characteristics. Further, a region which has an optical forbidden band gap narrower than that of the amorphous silicon forming the surface (or interface) region is disposed within the amorphous silicon layer to a thickness of at least 10 nm, whereby the sensitivity of the electrophotographic member to longer wavelengths of light can be enhanced.

What is claimed is: .[.1. In an electrophotographic member comprising at least a predetermined supporter having a conductive surface and an amorphous silicon layer which is electrically in contact with said conductive surface and which contains hydrogen and silicon as indispensable constituent elements thereof, the improvement comprising an amorphous silicon layer in which the silicon amounts to at least 50 atomic % and the hydrogen amounts to at least 1 atomic % and, at most, 50 atomic %, said amorphous layer comprising a first region and a second region, said first region being at least 10 nm thick, extending inwardly from an outer surface of said amorphous silicon layer and being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 10 10  Ω.cm, and said second region being located at least 10 nm from said surface of said amorphous layer, having a thickness of at least 10 nm, and being made of amorphous silicon which has an optical forbidden band gap that is smaller than that of said first region at the surface of the amorphous silicon and that is at least 1.1 eV..]. .[.2. An electrophotographic member according to claim 1, wherein said amorphous silicon layer is formed by a reactive sputtering process in an atmosphere containing hydrogen..]. .[.3. An electrophotographic member according to claim 1, wherein said amorphous silicon layer has a third region on a side opposite to said surface side formed by said first region, said third region being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 10 10  Ω.cm..]. .[.4. An electrophotographic member according to claim 1, wherein said amorphous silicon layer further contains at least one element selected from the group consisting of germanium and carbon which is substituted for silicon in an amount up to 
     
        30 atomic %..]. .[.5.  An electrophotographic member according to claim 1, wherein said member further comprises a conducter in contact with said amorphous silicon layer..]. .[.6. An electrophotographic member according to claim 1, wherein said supporter includes a substrate which is a conductive material and which is in contact with said amorphous silicon layer..]. .[.7. An electrophotographic member according to claim 1, wherein said supporter comprises an insulating substrate and a conductive electrode formed on said substrate and in contact with said amorphous 
     
     
        silicon layer..]. 8. .[.An.]. .Iadd.In an .Iaddend.electrophotographic member .[.according to claim 1,.]. .Iadd.comprising at least a predetermined supporter having a conductive surface and an amorphous silicon layer which is electrically in contact with said conductive surface and which contains hydrogen and silicon as indispensable constituent elements thereof, the improvement comprising an amorphous silicon layer in which the silicon amounts to at least 50 atomic % and the hydrogen amounts to at least 1 atomic % and, at most, 50 atomic %, said amorphous layer comprising a first region, a second region, and a third region, said first region being at least 10 nm thick, extending inwardly from an outer surface of said amorphous silicon layer and being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 10 10  5/8.cm;   said second region being located at least 10 nm from said surface of said amorphous layer, having a thickness of at least 10 nm, and being made of amorphous silicon which contains germanium and which has an optical forbidden band gap that is smaller than that of said first region at the surface of the amorphous silicon and that is at least 1.1 eV; and   said third region being located on a side opposite to said surface side formed by said first region and being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 10 10  Ω.cm, and .Iaddend.further comprising a layer on the side of the supporter in electrical contact with the amorphous silicon for   
     
     
        suppressing the injection of excess carriers from the supporter side. 9. .[.An.]. .Iadd.In an .Iaddend.electrophotographic member .[.according to claim 1,.]. .Iadd.comprising at least a predetermined supporter having a conductive surface and an amorphous silicon layer which is electrically in contact with said conductive surface and which contains hydrogen and silicon as indispensable constituent elements thereof, the improvement comprising an amorphous silicon layer in which the silicon amounts to at least 50 atomic % and the hydrogen amounts to at least 1 atomic % and, at most, 50 atomic %, said amorphous layer comprising a first region, a second region, and a third region, said first region being at least 10 nm thick, extending inwardly from an outer surface of said amorphous silicon layer and being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 10 10  Ω.cm;   said second region being located at least 10 nm from said surface of said amorphous layer, having a thickness of at least 10 nm, and being made of amorphous silicon which contains germanium and which has an optical forbidden band gap that is smaller than that of said first region at the surface of the amorphous silicon and that is at least 1.1 eV; and   said third region being located on a side opposite to said surface side formed by said first region and being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 10 10  Ω.cm, and .Iaddend.further comprising a layer for suppressing the injection of charges from the surface side of said   
     
     
        amorphous silicon layer. 10. An electrophotographic member according to claim 8 or claim 9, wherein said suppressing layer comprises a material which is SiO, SiO 2 , Al 2  O 3 , CeO 2 , V 2  O 3 , Ta 2  O, As 2  Se 3 , As 2  S 3 , or polyvinyl carbazole. .Iadd.11. An electrophotographic member according to claim 8 or claim 9, wherein said germanium is contained in said second region so that said amorphous silicon layer is sensitive to light of wavelengths longer than the long wavelength region of the visible light..Iaddend. .Iadd.12. An electrophotographic member according to claim 8 or claim 9, wherein said germanium is contained in said second region so that said amorphous silicon layer is sensitive to light of semiconductor laser..Iaddend. 
     
     
        .Iadd.3.  An electrophotographic member according to claim 8 or claim 9, wherein said germanium is substituted for silicon in an amount of up to 49 atomic %..Iaddend. .Iadd.14. An electrophotographic member according to claim 8 or claim 9, wherein at least one of said first region and said third region contains carbon which is substituted for silicon in an amount 
     
     
        up to 49 atomic %..Iaddend. .Iadd.15.  An electrophotographic member according to claim 8 or claim 9, wherein said amorphous silicon layer is formed by a reactive sputtering process in an atmosphere containing hydrogen..Iaddend. .Iadd.16. An electrophotographic member according to claim 8 or claim 9, wherein at least one of said first region and said third region further contains carbon which is substituted for silicon in an amount up to 30 atomic %..Iaddend. .Iadd.17. In an electrophotographic member comprising: at least a predetermined supporter having a conductive surface; and   an amorphous silicon layer being electrically in contact with the conductive surface, containing hydrogen and silicon as indispensable constituent elements thereof, the improvement comprising an amorphous silicon layer in which the silicon amounts to at least 50 atomic % and hydrogen amounts to at least 1 atomic % and, at most 50 atomic %, the amorphous silicon layer comprising a first, a second and a third region so as to form a narrow band gap region and wide forbidden band gap regions sandwiching the narrow forbidden band gap region, and the three regions are all intrinsic,   the first region as one of the wide band gap regions being at least 10 nm thick, extending inwardly from an outer surface of the amorphous silicon layer and being made of amorphous silicon containing carbon therein, and having an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 10 10  Ω.cm,   the second region as the narrow forbidden band gap region being located at least 10 nm from the surface of the amorphous silicon layer, having a thickness of at least 10 nm, and being made of amorphous silicon which has a optical forbidden band gap smaller than that of the first region at the surface of the amorphous silicon layer and that is at least 1.1. eV, and   the third region as the other wide forbidden band gap region being located so as to sandwich the second region cooperating with the first region, being made of amorphous silicon containing carbon therein, having an optical forbidden band gap of at least 1.6 eV and a resistivity of at   
     
     
        least 10 10  Ω.cm..Iaddend. .Iadd.18.  An electrophotographic member according to claim 17, wherein said amorphous silicon layer is formed by a reactive sputtering process in an atmosphere containing hydrogen..Iaddend. .Iadd.19. An electrophotographic member according to claim 17, further comprising a layer on the side of the supporter in electrical contact with the amorphous silicon for suppressing the injection of excess carriers from the supporter side..Iaddend. .Iadd.20. An electrophotographic member according to claim 17, further comprising a layer for suppressing the injection of charges from the surface side of said amorphous silicon layer..Iaddend. .Iadd.21. An electrophotographic member according to claim 17 or claim 18, wherein said suppressing layer comprises a material which is SiO, SiO 2 , Al 2  O 3 , CeO 2 , V 2  O 3 , Ta 2  O, As 2  Se 3 , As 2  S 3 , or polyvinyl carbazole..Iaddend. .Iadd.22. An electrophotographic member according to claim 17, wherein said second region has a resistivity less 
     
     
        than 10 10  Ω.cm..Iaddend. .Iadd.23.  An electrophotographic member according to claim 19, wherein said second region contains germanium..Iaddend.