Thermal and plasma damage in AlGaN Schottky diodes

The effects of pre-metallization plasma treatment and thermal annealing on the characteristics of Al x Ga 1− x N ( x ⩾ 0.25) Schottky diodes have been studied. Ar plasma treatment led to more rectifying electrical characteristics, suggesting that the near surface was compensated by ion-induced deep-level states. The maximum yet incomplete removal of the plasma damage was achieved after 800 °C annealing. Annealing at higher temperatures, however, resulted in further compensated surfaces and more rectifying diode characteristics. It has been found that Schottky contacts formed on thermally damaged AlGaN also exhibited increasingly rectifying characteristics as the annealing temperature was increased. These findings confirm that the energy levels of defects, including N vacancies, in AlGaN deepen as the Al mole fraction increases. Both plasma and thermal damage act as deep-level states in high-Al content AlGaN.