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

Abstract

The contact resistivity of transparent Pt contact on p-type GaN was drastically decreased by four orders of magnitude through the surface treatments in sequence, using aqua regia and (NH4)(2)S-x solution. The surface oxide on p-type GaN formed during epitaxial growth was removed in the boiling aqua regia, and the formation of native oxide on the oxide-free surface during air exposure prior to metal deposition was suppressed by the (NH4)(2)S-x treatment. This suggests that the reduction of contact resistivity is due to direct contact of Pt on the clean: surface of p-type GaN. via shift of the Fermi level to a energy level of accepters near the valence band, resulting in the reduction of barrier height for holes at the interface of Pt/p-type GaN.