The properties of Si-doped GaN films which had been grown onto multiple AlN interlayers, sandwiched between high-temperature GaN, were presented. It was shown that, as the number of layers increased, the electron mobility increased in the top Si-doped GaN layer. Cross-sectional transmission electron microscopy revealed an appreciable reduction in the screw dislocation density in GaN films that were grown onto the AlN/GaN layers. The symmetrical and off-axis X-ray line-widths increased as the number of layers increased; thus indicating a greater relative misalignment of the adjacent GaN layers. An analysis which was based upon a single-donor/single-acceptor model for the electrical conduction suggested that the improved electron mobility was the result of a reduced acceptor concentration in the top GaN film, and that this acceptor might be associated with threading screw dislocations in GaN.

Properties of Si-Doped GaN Films Grown using Multiple AlN Interlayers. D.D.Koleske, M.E.Twigg, A.E.Wickenden, R.L.Henry, R.J.Gorman, J.A.Freitas, M.Fatemi: Applied Physics Letters, 1999, 75[20], 3141-3