Room-temperature Ohmic contact on <i>n</i>-type GaN with surface treatment using Cl2 inductively coupled plasma

A room-temperature Ti/Al Ohmic contact on n-type GaN was obtained by surface treatment using Cl2 inductively coupled plasma treatment. The specific contact resistivity was dramatically decreased from the Schottky behavior to 9.4×10−6 Ω cm2 by the treatment. The binding energy of the Ga–N bond and the atomic ratio of Ga/N were simultaneously increased after the plasma treatment. This provides evidence that N vacancies, acting as donors for electrons, were produced at the etched surface, resulting in a shift of the Fermi level near to the conduction band. This leads to the reduction in contact resistivity through the decrease of the Schottky barrier for the conduction of electrons.