Reduction of ohmic contact resistivity on p-type GaN by surface treatment

The pre-treatment of p-type GaN surface using boiling aqua regia was effective in reducing oxygen and carbon, which plays a critical role in decreasing contact resistivity of Pt contact on p-type GaN. The treatment caused the shift of the surface Fermi level of p-type GaN and subsequent to the reduction of band bending below the contact. The results suggest that the pre-treatment plays a role in removing the surface oxides, leading to the reduction of barrier height for the transport of holes at the interface of metal with p-type GaN.