Abstract
This study made use of graphene and amorphous silicon in order to fabricate a heterojunction photodetector, in which controlling the thickness and doping properties of the amorphous silicon film allows for fine-tuning of the photodetector properties. The device response to different light intensities were characterized. Graphene was grown via APCVD using a gaseous carbon source in an Argon atmosphere, in which controlling the carrier gas flow and growth time has a direct impact on the quality of the as-grown graphene film. On the other hand, the amorphous silicon layer was grown using PECVD under different conditions. For this film, changes in the doping condition allow for different wavelength light absorption properties, in order to achieve an optimum light absorption. The fabricated photodetector mainly consists of a junction between a single monolayer graphene sheet and a 300nm thick intrinsic amorphous silicon layer, a 270nm thick intrinsic amorphous silicon layer plus a 30nm N-doped amorphous silicon thin film, or a 170nm thick intrinsic amorphous silicon layer plus a 30nm N-doped amorphous silicon layer. At both sides of the junction, ohmic contacts are deposited. In order to avoid undesired influences from the contacts and to quantify their influence, the conduction property of the contacts, which include the junctions between graphene and gold, aluminum and amorphous silicon, as well as probe needles and amorphous silicon, is characterized. Thus the properties of the graphene and amorphous silicon junction can be correctly derived from the measurements.