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

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.