Thermal stability and barrier height enhancement for refractory metal nitride contacts on GaAs

Self-aligned GaAs metal-semiconductor field-effect transistor process requires a very thermally stable gate material which must maintain good Schottky contact with GaAs after high-temperature annealing. The electrical characteristics of rf-sputtered ZrN, TiN, and NbN contacts on n-GaAs substrate have been investigated as a function of annealing temperature. We show that all these refractory metal nitride contacts on GaAs have ideality factors very close to unity after annealing at temperatures as high as 850 °C. The barrier height for these contacts increases with annealing temperature and very low reverse leakage current is obtained. We also observe similar behavior from previous work on WN/GaAs contacts. Such barrier height enhancement at elevated temperatures has been attributed to the incorporation of nitrogen into GaAs near the metal/GaAs interface.