Investigations of ohmic contacts to reactive-ion-etched p-type GaN

This paper will detail investigations into rapid thermal annealing (RTA) treatment of ohmic contacts to reactive ion etch (RIE) damaged p-type GaN. It was found that annealing at moderate temperatures in N-2 atmosphere can improve the ohmic nature of contacts to RIE-damaged p-GaN. After chlorine-based RIE treatment of the p-GaN surface the sheet resistance and contact resistivity of the ohmic contact metallisation scheme increased, and the contacts became extremely non-ohmic. After RTA treatment in N-2 atmosphere at 550degreesC, linearity of the I-V curves was substantantially improved, and the contact resistivity decreased. This improvement is most likely related to improvements in the metal-GaN interface and/or improvements in the bulk material when protected by the contact metal. Unprotected surfaces were further damaged (manifested as higher sheet resistance) by the annealing procedure.