Thin Multi-Layered Photoreceptor Deposited from Disilane
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Thin Multi-Layered Photoreceptor Deposited From Disilane S. Araki, H. Nou, H. Kamaji, and K. Kiyota Peripheral Devices Laboratory, Fujitsu Laboratories Kamikodanaka, Nakaharaku, Kawasaki 211, Japan
Ltd.
Kawasaki,
1015,
ABSTRACT A thin multi-layered photoreceptor drum has been fabricated, using The photoreceptor is thin(10 glow-discharge decomposition of disilane. The photoreceptor has three pm), but it is charged up sufficiently. layers; the p-type a-Si:H (blocking layer), the intrinsic B-doped a-Si:H (photoconductive layer) and a-SiC:H (passivation layer). Disilane is highly reactive. The intrinsic B-doped a-Si:H was prepared from a slightly gaseous mixture of B2 H6 (3 ppm). The amorphous-SiC:H passivation layer deposited
from
Si2H6 and C3H8 was developed to achieve sufficient surface
potential and to improve the environmental characteristics. Introduction Nowadays, amorphous Si photoreceptors are gradually replacing selenium photoreceptors[1J. However, problems of manufacture and stability in humid environments remain to be solved. In an attempt to solve these problems, we tried to fabricate a multi-layered photoreceptor[2] by two distinct techniques. Firstly, highly reactive disilane[3] was used as a host gas. We could realize the boron doped a-Si layers with a low ratio of diborane and low plasma damage. These are advantageous to decrease the number of defects of a-Si:H. Secondly, amorphous silicon carbide was deposited from disilane and propane and was applied to a passivation layer. There are many reports concerning the combination of monosilane and the carbon source gases[4,5]. We succeeded in fabricating a good a-SiC film deposited from disilane and propane, and achieved good environmental characteristics. The structural, optical and electrical properties of a-SiC:H are dependent upon carbon and silicon sources and deposition conditions[4,5J. This time, we deposited a-SiC:H films in several ratios of C3 H8 /(C 3 H8 +Si 2 H6 ) and measured their properties. Structure of a-Si photoreceptor The dark conductivity of a-Si is high, so a multi-layered structure must be used. The photoreceptor has three layers; a blocking layer, a photoconductive layer, and a passivation layer. The blocking layer is highly doped with boron. The doping gas ratio, B2 H6 /Si 2 H6 , is 140 ppm for the p+ layer. Its thickness is 0.6 pm. The photoconductive layer is only slightly doped with boron. The doping gas ratio is 3 ppm for the intrinsic layer. The thickness is 11 ,m. The passivation layer is a-SiC. The passivation layer is used not only for protection but also for blocking. Its thickness is 0.3,um. Table 1 shows the deposition parameters. Both the flow rate and RF power are low.
Mat. Res. Soc. Symp. Proc. Vo. 70ý , 1986 Materials Research Society
678
Table 1 Deposition parameters
Range Parameter a-SiC: H
a-Si:H (B)
100 W
RF power
200 W
Pressure
400 Pa B2 H 6 /He 1H 00 ppm
Gas
Si2
6
Flow rate I00 sccm
400 Pa H6 C3 He S2
0-100
15 sccm
3-200 sccm
sccm
B doped a-Si:H layers Figure 1 shows the photo and dar
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