Schottky barrier diodes, on the Ga or N faces of an approximately 300μm-thick free-standing GaN layer (grown via hydride vapour-phase epitaxy followed by laser separation), were studied by means of capacitance-voltage and deep-level transient spectroscopy. A 1/C2 versus V analysis showed that the barrier heights of Ni/Au Schottky contacts were different for the two polar faces (1.27eV for the Ga face, 0.75eV for the N face). In addition to the 4 common deep level transient spectroscopy traps which had been observed previously in other epitaxial GaN samples, including hydride vapour-phase epitaxially-grown GaN, a new trap (B') with an activation energy of 0.53eV was found in Ga-faced samples. Another trap (with an activation energy of 0.18eV), which was believed to be related to the N vacancy, was found in N-faced samples. A further trap (with an activation energy of 0.35eV) was found in Ga-faced samples. The latter trap was suggested to have arisen from reactive-ion etching damage.

Deep Centres in a Free-Standing GaN Layer. Z.Q.Fang, D.C.Look, P.Visconti, D.F.Wang, C.Z.Lu, F.Yun, H.Morkoç, S.S.Park, K.Y.Lee: Applied Physics Letters, 2001, 78[15], 2178-80