Schottky diode measurements of dry etch damage in n- and p-type GaN

Abstract

n- and p-type GaN was exposed to inductively coupled plasma of ${\mathrm{N}}_2,$ ${\mathrm{H}}_2,$ Ar, or ${\mathrm{Cl}}_2/\mathrm{Ar},$ as a function of source power (0–1000 W) and rf chuck power (20–250 W). For n-GaN, there was a strong reduction in diode reverse breakdown voltage and an increase in forward and reverse currents, while for p-GaN the reverse breakdown voltage increased. These results are consistent with creation of point defects with shallow donor nature that increase the conductivity of initially n-type GaN or decrease the conductivity of p-type GaN. Annealing at 750 °C under ${\mathrm{N}}_2$ produced significant recovery of the electrical properties, while wet etch removal of 500–600 Å of the surface produced a full recovery. For completed n-type mesa diodes exposed to Ar or ${\mathrm{Cl}}_2/\mathrm{Ar}$ discharges, the low bias forward currents increased by several orders of magnitude. The exposed surfaces became ${\mathrm{N}}_2$ deficient in all cases.