Ohmic contacts of ZnO/SnO2 equal-cosubstituted In2O3 films to n-InP and p-GaAs

Abstract

ZnO/SnO₂ equal-cosubstituted In₂O₃ (ZITO) films were deposited by ion beam assisted deposition onto n-InP and p-GaAs substrates. Rapid contact annealing processes (RCP) at different temperatures were done to study the thermal stability of their interfacial contact properties between ZITO films and the semiconductor substrates. Oxygen flow rate during deposition is the main tuning parameter for ZITO films growth. Highest conductivity for ZITO film deposited at the oxygen flow rate of 0 sccm (ZITO-0) was got at 525.2 S cm⁻¹; lowest optical loss at wavelength of 1550 nm for ZITO film prepared at the oxygen flow rate of 7 sccm (ZITO-7) was obtained at 592.7 cm⁻¹. Ohmic contacts have been achieved between ZITO films and n-InP pretreated both by hydrogen plasma and by oxygen plasma (H₂-cleaned n-InP and O₂-cleaned n-InP). The contact between ZITO-0 film and H₂-cleaned n-InP substrate shows good thermal stability in RCP, the specific contact resistivity of 1.84 × 10⁻⁴ Ω cm² for as-deposited ZITO-0 film contact to H₂-cleaned n-InP and 1.24 × 10⁻⁴ Ω cm² for the one annealed at 450 °C. While, RCP at proper temperature (360 °C and 400 °C) is the key to achieve ohmic contact between ZITO-0 film to H₂-cleaned p-GaAs substrate.