Low resistance Ti/Al/Ni/Au Ohmic contact to (NH4)2Sx treated n-type GaN for high temperature applications

Low resistance Ti/Al/Ni/Au Ohmic contact to (NH₄)₂S_x treated n-type GaN has been studied in the temperature range from 25°C to 600°C It is found that the specific contact resistivity ¿_c of the sample treated with (NH₄)₂S_x solution for 5 min at 90°C decreases with increasing measuring temperature, while the ¿_c of the sample treated with (NH₄)₂S_x solution for 25 min at 90°C increases with increasing measuring temperature. Excellent agreement with the ¿5 min-treated¿ sample can be obtained by the field emission model with an average Schottky barrier height (SBH) ¿_B=1.05 eV. Meanwhile, a field emission model with a temperature-dependent effective SBH is suggested to be responsible for the ¿25 min-treated¿ sample in which metal/semiconductor (MS) interface potential pinch-off may occur.