Recovery of Dry-Etch Damage in Gallium-Nitride Schottky Barrier Diodes

We investigated the effects of recovery schemes on the characteristics of GaN Schottky diodes damaged by inductively coupled Cl₂/H₂/Ar/CH₄ plasma etching. The recovery schemes included N₂ plasma exposure, N₂ plasma plus annealing at 600°C in N₂. and annealing at 700°C in N₂. Ga-deficient GaN surface layers were observed after etching the GaN, and the Ga/N stoichiometry at the surface was most strongly affected by the Cl₂ flow rate among the process variables. The samples annealed at 700°C showed a clear improvement in diode characteristics and a complete restoration of the Ga/N ratio from ca. 0.87 to ca. 1.0 at the surface layers, as measured by Auger electron spectroscopy. For all other damage-recovery schemes, the samples showed no significant enhancement in diode characteristics and incomplete restoration of Ga/N stoichiometry at the surface layers.