Evaluation of NiInNi multi-layers for thermally stable ohmic contacts to n-GaAs

A thermally stable, low resistance ohmic contact system NiInNi to n-GaAs was investigated. The lowest value of the specific contact resistance ϱc was 1.71 × 10−4 Ω cm2. Heating the contact up to 400 °C for 5 h did not obviously change the value of ϱc. It was observed by Auger electron spectroscopy and X-ray diffraction that NiIn compounds, GaNi and InAs formed at the metal-GaAs interface. It was noted that In reacted with GaAs and formed a heterojunction ohmic contact (such as InAs-InxGa1−xAs-GaAs) and due to the low melting point (156 °C) of In, additions of Ni are needed to completely react the remaining In to form a high melting point compound.