Investigation of Different Metals as Ohmic Contacts to β-Ga2O3: Comparison and Analysis of Electrical Behavior, Morphology, and Other Physical Properties

Nine metals (Ti, In, Ag, Sn, W, Mo, Sc, Zn, and Zr) have been investigated as electrical contacts to n-type single-crystal β-Ga2O3 substrates as a function of annealing temperature up to 800°C (in flowing Ar). For each contact metal, we investigated its electrical behavior and morphology at each annealing temperature, as well as the effects of adding a Au capping layer. Select metals displayed either ohmic (Ti and In) or pseudo-ohmic (Ag, Sn, and Zr) behavior under certain conditions; however, the morphology was often a problem. It was concluded that metal work function is not a dominant factor in forming an ohmic contact to β-Ga2O3 and that limited interfacial reactions play an important role.