Non-alloyed Cr/Au Ohmic contacts to N-face and Ga-face n-GaN

Abstract Non-alloyed Cr/Au Ohmic contacts on N-face and Ga-face n-GaN were studied. The specific contact resistances ( ρ c ) of Cr/Au contacts onto the N-face and Ga-face n-GaN were as low as 2.4 × 10 −4  Ω cm 2 and 2.4 × 10 −5  Ω cm 2 , respectively. Native oxide formed on the n-GaN surface was believed to be the key factor for higher ρ c . The results of X-ray photoelectron spectroscopy confirmed that n-GaN samples with different surface polarities or treated by different chemical solutions exhibited significant differences in gallium oxide content on the surface, which led to a marked difference in the ρ c of non-alloyed Cr/Au Ohmic contacts to GaN films.