Transparent Pt ohmic contact on p-type GaN with low resistivity using (NH4)(2)S-x treatment

Abstract

The contact resistivity of transparent Pt contact on p-type GaN was drastically decreased from (5.1 +/- 0.6) x 10(-1) Omega cm(2) to (2.5 +/- 0.3) x 10(-5) W cm(2) by the surface treatments in sequence using aqua regia and (NH4)(2)S-x solution. The aqua regia plays a role in removing the surface oxide formed on p-type GaN during epitaxial growth, and the (NH4)(2)S-x protects the clean surface from the formation of native oxide during air exposure. The reduction of contact resistivity is due to direct contact of Pt to the clean surface of p-type GaN, via shift of the Fermi level position to an energy level near the valence band, resulting in the reduction of barrier height for holes at the interface of Pt/p-type GaN. (C) 1999 The Electrochemical Society. S1099-0062(99)08-131-6. All rights reserved.