I-V and C-V studies of evaporated amorphous arsenic telluride film on crystalline silicon

Abstract

The I-V characteristics of amorphous arsenic telluride (As₂Te₃) thin film on single-crystalline silicon substrates exhibit similarity with the characteristics of a heterojunction formed between crystalline semiconductors and the carrier transport, which involves more than one conduction mechanism at the interface. The recombination, tunnelling, and space-charge-limited carrier transport takes place at the interface successively, depending on the magnitude of the applied voltage. The heterojunction properties dominate at lower voltages (below 1 V), while at the higher voltages, the I-V characteristic is determined by the As₂Te₃ film. The temperature-dependent I-V characteristics confirm the formation of a heterojunction at the silicon-As₂Te₃ (film) interface. The built-in potential evaluated from the I-V characteristics (~0.2 V) agrees well with the observed open-circuit photovoltage Voc. Contrary to the I-V characteristics, the C-V characteristics resemble the characteristics of a conventional metal-insulator-semiconductor (MIS) structure. This can be qualitatively explained by assuming the heterojunction to have a low breakdown potential (~1.0 V), and the junction barrier capacitance in the breakdown region to be higher than either the film or the depletion capacitance.