Thermal stability of Ti/Pt/Au nonalloyed ohmic contacts on InN

Abstract

Extremely low contact resistance of nonalloyed Ti/Pt/Au metallization on n‐type InN is demonstrated. The contacts were annealed at different temperatures up to 420 °C to investigate their thermal stability. A low contact resistivity of 1.8×10⁻⁷ Ω cm² was measured at room temperature using the transmission line method. This was due to the extremely high doping level (5×10²⁰ cm⁻³) in the InN. After 300 °C annealing, the contact resistivity increased to 2.4×10⁻⁷ Ω cm². For 360 °C annealing, the contact morphology showed some degradation, but the contact resistivity was almost the same as at 300 °C. There was serious degradation of the contacts after 420 °C annealing. The morphology became very rough, and the contact and sheet resistances increased by factors of 3–5 times. This degradation is believed due to the decomposition of the InN film. The contact resistivities between n‐type epitaxial GaAs and InN were also investigated, and showed values around 10⁻⁴ Ω cm².