Improvement of n-GaN Schottky diode rectifying characteristics using KOH etching

KOH etch was investigated as a means to improve the I–V characteristics of Schottky diodes on n-type GaN grown by molecular-beam epitaxy on sapphire, or on hydride vapor phase epitaxy templates. Atomic force microscopy images and I–V characteristics are presented. After etching as-grown films in molten KOH, Schottky diodes on c-plane GaN had orders of magnitude reduction in reverse leakage current. The best devices had leakage currents less than 10−12 A (10−8 A/cm2) at −5 V, and ideality factors of 1.04. Measurements on several different sample structures indicate a correlation between surface roughness and saturation current, and an improvement in ideality factor when etched in KOH. Phosphoric acid was also investigated, but did not result in significant improvements in I–V characteristics.