Effect of Argon Ion Irradiation on Ohmic Contact Formation on n-type Gallium Nitride

Abstract

This paper describes electrical properties at the interface between n-type GaN and Ti contact layers formed by RF magnetron sputter deposition under various time of Ar⁺ irradiation. The conductance increases proportionately to the extension of the Ar⁺ irradiation time, indicating that Ar⁺ irradiation enhances the formation of nitrogen vacancies and consequently Schottky barrier width is narrowed. On the other hand, extensive Ar⁺ irradiation for 3600 s and longer does not show further increase of conductance. Extensive selective sputtering of nitrogen atoms out of GaN has induced the phase transformation from GaN to Ga at the surface of GaN. The Ga phase enhances the formation of Ga–Ti compounds during the deposition of Ti, and it increases the height and width of the Schottky barrier.