Near-Surface Type Conversion of p-type Single-Crystal InP by Plasma Exposure,

During the past several years considerable work has gone into describing why a buried homojunction forms during direct current dc magnetron sputter deposition of indium tin oxide ITO on single-crystal, p-type InP. Several mechanisms have been suggested to account for the resulting device behavior. Bachmann suggested that type conversion may be due to substitutional doping by Sn, while Tsai et al. believed that sputter damage was a possibility. In our own work, Sn-free ln2O3 was substituted for the ITO, resulting in devices with very similar photovoltaic response to their ITOInP counterparts, indicating that Sn is not the cause of type conversion. To investigate this junction formation process further, photovoltaic solar cells have been fabricated by exposing p-type InP substrates to a pure hydrogen plasma without any deposition procedure involved. In this paper we report how this H2 plasma exposure PE affects the InP surface properties. The results confirm that deposition is not necessary to cause the type conversion which forms the buried homojunction, and suggest a fabrication process that may be useful with other relevant materials.