Thermally stable Pd/Sn and Pd/Sn/Au ohmic contacts to n-type GaAs

Abstract

Thermal stability of novel Pd/Sn and Pd/Sn/Au Ohmic contacts to n-GaAs has been investigated and compared to the non-alloyed Pd/Ge and alloyed Au–Ge/Ni metallizations. Metallization samples are furnace annealed at various temperatures and systematically characterized utilizing Scanning Electron Microscopy (SEM) and current–voltage (I–V) measurements. Contact resistivities, ρ c , of the proposed metallization are measured using a conventional Transmission Line Model (cTLM) method. The Pd/Sn Ohmic contacts display superior thermal stability at 410 °C when compared to the Pd/Ge contacts. After annealing at 410 °C for 4 h, p c of the Pd(50 nm)/Sn(l25 nm) metallization remains in the low 10 –5 Ω cm 2 range, whereas ρ c values increase to 10 –4 Ω cm 2 for the Pd(50 nm)/Ge(l26 nm) contacts. At 410 °C, the Pd/Sn/Au metallizations also display better thermal stability than that of non-alloyed Pd/Ge and alloyed Au–Ge/Ni metallizations. The long-term stability at 300 °C of the Pd/Sn and Pd/Sn/Au Ohmic contacts is also reported.