Low-Resistance Ti/Au Ohmic Contact on (001) Plane Ga 2 O 3 Crystal

We studied the Ti/Au Ohmic contact on (001) plane Ga 2 O 3 single crystal wafer as a function of annealing temperature and crystallographic orientation. The lowest specific contact resistances of ∼5 × 10 −4 Ω·cm 2 were obtained at 400 °C annealing temperature under nitrogen ambience. The Ohmic metal contact became degraded when annealed above 500 °C. The formation of Ti oxide might be responsible for the degradation of Ohmic contact at high annealing temperatures. In comparison with (010) Ga 2 O 3 substrate, the Ohmic contact could be more easily formed on ( 2 ¯ 01 ) and (001) Ga 2 O 3 planes, possibly due to high surface energy and dangling bond density. It is notable that the contact properties did not show any particular dependence on in-plane azimuth angles on (001) Ga 2 O 3 substrate.