The use of amorphous-crystalline silicon heterojunctions for the application to an imaging device

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Abstract
Experiments on p‐type hydrogenated amorphous silicon (a‐Si:H)/n‐type crystalline silicon (c‐Si) heterojunctions were performed to determine the suitability of their application to an imaging device. Optoelectrical properties such as current voltage (I‐V), capacitance voltage (C‐V), and spectral photoresponses were measured in the a‐Si:H/c‐Si heterojunctions prepared with or without a mesh used to keep the glow‐discharge plasma away from the c‐Si substrate. The C‐V characteristics revealed that there was something (probably interface defect states) obstructing the spread of the depletion layer in c‐Si at the interface of a‐Si:H and c‐Si when c‐Si was exposed in the glow‐discharge plasma during the deposition of a‐Si:H; the C‐V characteristics also revealed that the origin of the interface defect states was considered to be due to the damage of c‐Si caused by the positive‐ion bombardment from the plasma at the initial stage of the deposition of a‐Si:H. In a‐Si:H/c‐Si junctions with few interface defect states, the spectral photoresponses and I‐V characteristics showed a wide photoresponse, good photocurrent characteristics, and a low dark current in the reverse bias. A new Si target without a diode array was demonstrated to be of high quality for the application of this heterojunction to an imaging device.