THE THERMAL-STABILITY OF INDIUM TIN OXIDE/N-GAAS SCHOTTKY CONTACTS

Indium-tin-oxide (ITO) is a wide band gap degenerately doped semiconductor which forms a rectifying heterojunction with GaAs. The interface exhibits electrical characteristics which parallel those of conventional metal/semiconductor Schottky diodes. The combination of properties - high visible transparency and high electrical conductivity - opens up interesting electro-optical applications for the material. New results are presented on the transport mechanism in ITO layers and the ITO/GaAs interface. Thermal stressing of ITO/GaAs shows that the basic system degrades at relatively low temperatures. The mechanism of degradation is the near interface n+ doping of GaAs by the interdiffusion of Sn and/or In from the ITO into GaAs. These results have important consequences for device applications such as solar cells which operate at temperatures in excess of 100-degrees-C.