The effects of pre-metallization annealing on the electrical characteristics of GaN

and AlxGa1−xN (x = 0.25 and 0.5) Schottky diodes were studied. Annealing above

800 C in an Ar ambient led to a significant preferential N loss, and annealing at

1000 C 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 donorlike

vacancies in GaN, N vacancies in AlGaN with an Al mole fraction greater than

25% behaved as deep-level states, compensating the near-surface region. Care

therefore had to 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