The effects of pre-metallization annealing upon the electrical characteristics of GaN and AlxGa1−xN (x = 0.25 and 0.5) Schottky diodes were studied. Annealing above 800C in an Ar ambient led to a significant preferential N loss, and annealing at 1000C caused localized surface decomposition. The Pt/Au Schottky contacts on the annealed GaN became leakier, whereas those on the thermally damaged AlGaN exhibited more rectifying characteristics. Prolonged annealing produced more conductive AlGaN surfaces deficient in both N and Al, as revealed by X-ray photoelectron spectroscopy. These findings suggested that, as opposed to donor-like vacancies in GaN, N vacancies in AlGaN with an Al mole fraction ≥ 25% behave as deep-level states, compensating the near-surface region. Care must therefore be taken to prevent the loss of N during thermal processing of high-Al content AlGaN.

Investigation of the Electronic Properties of Nitrogen Vacancies in AlGaN. X.A.Cao, A.A.Syed, H.Piao: Journal of Applied Physics, 2009, 105[6], 063707