Low-resistance Ti-based ohmic contacts on p-GaAsSb

Ohmic contacts based with TiN (8 nm)/Ti (10 nm) metallization provide a thermally stable, low-resistance electrical interface to GaAsSb on InP. The ohmic behavior is electrically characterized using the transmission line method (TLM). An extremely low specific contact resistivity is achieved, with ρ c = 2 × 10 −5 Ω cm 2 up to 450 °C after a two-step annealing process for the lift-off approach, and ρ c ∼ 2 × 10 −6 Ω cm 2 for dielectric-encapsulated processes. Microstructural characterization of the metal-semiconductor interface is performed using X-ray diffraction (XRD), Time-of-Flight Secondary Ion Mass Spectrometry (ToFSIMS) and Transmission Electron Microscopy (TEM). Thermal degradation of the contact for temperatures above 450 °C in the lift-off process is attributed to Ti in-diffusion and Ga, As and Sb out-diffusion, which indicates significant elemental redistribution at 500 °C and the possible formation of a Ti-As-Sb intermixed layer at the GaAsSb interface.