The effects of reactive ion etching-induced damage on the characteristics of ohmic contacts to n-type GaN

The effects of reactive ion etching n-GaN surfaces with both SiCl₄ and Ar plasmas have been investigated using transmission line measurements. The measurements were made from ohmic contacts consisting of Al (as-deposited) and Ti/Al (as-deposited and rapid thermal annealed). The contact resisitance, specific contact resistance, and sheet resistance were investigated as functions of the dc plasma sel dias voltage and etch time. The contact resistance extracted from contacts fabricated on surfaces etched with SiCl₄ was found to be improved over the unetched samples for all conditions investigated. Dry etching the surface with Ar severely degraded the contact resistance over the unetched sample except at the lower self-bias voltages. Rapid thermal annealing of etched samples prior to Al deposition was found to be effective in removing some of the reactive ion etching/SiCl₄-induced damage.