Photoreceptor with improved blocking layer

Abstract

A photoreceptor includes a multilayer blocking structure to reduce dark discharge of the surface voltage of the photoreceptor resulting from electron injection from an electrically conductive substrate. The multilayer blocking structure includes wide band gap semiconductor layers in alternating sequence with one or more narrow band gap blocking layers. A fabrication method of the photoreceptor includes transfer-doping of the narrow band gap blocking layers, which are deposited in alternating sequence with wide band gap semiconductor layers to form a blocking structure. Suppression of hole or electron injection can be obtained using the method.

What is claimed is: 
     
         1 . A photoreceptor comprising:
 a photoconductor layer comprising a photosensitive material;   an electrically conductive substrate layer, and   a multilayer blocking structure between the substrate layer and the photoconductor layer, the blocking structure including first and second wide band gap semiconductor layers and a narrow band gap blocking layer between and adjoining the first and second wide band gap semiconductor layers, the narrow band gap blocking layer being effective to suppress electron or hole injection from the electrically conductive substrate into the photoconductor layer.   
     
     
         2 . The photoreceptor of  claim 1 , further including a passivation layer on the photoconductor layer. 
     
     
         3 . The photoreceptor of  claim 1 , wherein the photoconductor layer is comprised of a hydrogenated semiconductor material. 
     
     
         4 . The photoreceptor of  claim 3 , wherein the photoconductor layer is comprised of hydrogenated amorphous silicon (a-Si:H). 
     
     
         5 . The photoreceptor of  claim 4 , wherein the photoconductor layer includes a nanocrystalline or microcrystalline portion. 
     
     
         6 . The photoreceptor of  claim 4 , wherein the narrow gap blocking layer is comprised of hydrogenated amorphous germanium (a-Ge:H), hydrogenated amorphous silicon germanium (a-SiGe:H), hydrogenated nanocrystalline germanium (nc-Ge:H), hydrogenated nanocrystalline silicon-germanium (nc-SiGe:H), hydrogenated nanocrystalline silicon (nc-Si:H), hydrogenated nano-crystalline germanium oxide (nc-GeO:H) or hydrogenated nano-crystalline silicon-germanium oxide (nc-SiGeO:H). 
     
     
         7 . The photoreceptor of  claim 4 , wherein the first wide band gap semiconductor layer is comprised of a material selected from the group consisting of a-SiC:H, a-SiO:H, a-SiN:H, nc-SiC:H, nc-SiO:H, nc-SiN:H, and a combination thereof. 
     
     
         8 . The photoreceptor of  claim 4 , wherein the photoconductor layer is doped slightly p-type and the narrow band gap blocking layer is a p+ layer effective for suppressing electron injection into the photoconductor layer. 
     
     
         9 . The photoreceptor of  claim 4 , wherein the blocking structure includes a plurality of narrow band gap blocking layers, each blocking layer comprising a-Ge:H, a-SiGe:H, nc-Ge:H, nc-SiGe:H, nc-Si:H, nc-GeO:H or nc-SiGeO:H and adjoining a pair of wide band gap semiconductor layers. 
     
     
         10 . The photoreceptor of  claim 9 , wherein one or more of the wide band gap semiconductor layers are comprised of a material selected from the group consisting of a-SiC:H, a-SiO:H, a-SiN:H, nc-SiC:H, nc-SiO:H, nc-SiN:H or a combination thereof. 
     
     
         11 . The photoreceptor of  claim 9 , wherein each of the narrow band gap blocking layers has a thickness between 3-30 nm and each of the wide band gap semiconductor layers has a thickness between 5-25 nm. 
     
     
         12 . The photoreceptor of  claim 11 , wherein the total thickness of the narrow band gap blocking layers is less than 75 nm and the total thickness of the wide band gap semiconductor layers is less than 50 nm. 
     
     
         13 . The photoreceptor of  claim 1 , wherein the narrow band gap blocking layer is an n+blocking layer effective to suppress hole injection into the photoconductor layer. 
     
     
         14 . The photoreceptor of  claim 1 , wherein one of the wide band gap semiconductor layers adjoins the electrically conductive substrate layer and another of the wide band gap semiconductor layers adjoins the photoconductor layer. 
     
     
         15 . The photoreceptor of  claim 1 , wherein one of the wide band gap semiconductor layers adjoins the electrically conductive substrate layer and another of the wide band gap semiconductor layers adjoins the photoconductor layer. 
     
     
         16 . The photoreceptor of  claim 15 , wherein the narrow band gap blocking layer comprises a-Ge:H, a-SiGe:H, nc-Ge:H, nc-SiGe:H, nc-Si:H, nc-GeO:H or nc-SiGeO:H, and one or more of the wide band gap semiconductor layers are comprised of a-SiC:H, a-SiO:H, a-SiN:H, nc-SiC:H, nc-SiO:H, or nc-SiN:H, or a combination thereof. 
     
     
         17 . A photoreceptor comprising:
 a photoconductor layer comprising a photosensitive material;   an electrically conductive substrate layer, and   a multilayer blocking structure between the photoconductor layer and the electrically conductive layer, the multilayer blocking structure comprising:
 a plurality of wide band gap semiconductor layers, and 
 one or more narrow band gap blocking layers having band gaps smaller than those of the wide band gap semiconductor layers, the one or more narrow band gap blocking layers and the plurality of wide band gap semiconductor layers being arranged in alternating sequence, the one or more narrow band gap blocking layers being effective to suppress electron or hole injection from the electrically conductive substrate layer. 
   
     
     
         18 . The photoreceptor of  claim 17 , wherein the photoconductor layer is comprised of a hydrogenated amorphous or nanocrystalline semiconductor layer and the one or more narrow band gap blocking layers are p+ layers effective for suppressing electron injection into the photoconductor layer. 
     
     
         19 . The photoreceptor of  claim 17 , wherein the photoconductor layer is comprised of hydrogenated amorphous silicon. 
     
     
         20 . The photoreceptor of  claim 19  wherein the narrow band gap blocking layer is comprised of hydrogenated amorphous germanium (a-Ge:H), hydrogenated amorphous silicon germanium (a-SiGe:H), hydrogenated nanocrystalline germanium (nc-Ge:H), hydrogenated nanocrystalline silicon-germanium (nc-SiGe:H), hydrogenated nanocrystalline silicon (nc-Si:H), hydrogenated nano-crystalline germanium oxide (nc-GeO:H) or hydrogenated nano-crystalline silicon-germanium oxide (nc-SiGeO:H). 
     
     
         21 . The photoreceptor of  claim 19 , wherein one or more of the wide band gap semiconductor layers are comprised of a-SiC:H, a-SiO:H, a-SiN:H, nc-SiC:H, nc-SiO:H, or nc-SiN:H, or a combination thereof. 
     
     
         22 . The photoreceptor of  claim 19 , wherein each of the one or more narrow band gap blocking layers has a thickness between 3-30 nm. 
     
     
         23 . The photoreceptor of  claim 22 , further including more than one narrow band gap blocking layer, the combined thickness of the narrow band gap blocking layers being less than 75 nm and the combined thickness of the wide band gap semiconductor layers totals less than 50 nm. 
     
     
         24 . The photoreceptor of  claim 17 , wherein the photoconductor layer is comprised of hydrogenated amorphous silicon and further wherein one of the wide band gap semiconductor layers adjoins the electrically conductive substrate layer and another of the wide band gap semiconductor layers adjoins the photoconductor layer. 
     
     
         25 . The photoreceptor of  claim 17 , wherein one of the wide band gap semiconductor layers adjoins the electrically conductive substrate layer and another of the wide band gap semiconductor layers adjoins the photoconductor layer.