Effect of AlN buffer layer deposition conditions on the properties of GaN layer

The effects of deposition conditions of AIN buffer layers upon the properties of the high-temperature GaN layers, such as crystallinity, surface morphology and polarity, were investigated. When the deposition temperature became high, the hexagonal-faceted surface morphology was observed, and hence the growth direction was estimated to be (0 0 0 1)N surface from the experimental results shown in our previous papers. The surface morphology and hence the polarity of the GaN layer was found to change by modifying the gas-flow timing of the TMA1 and NH3. The smooth surface was obtained for a V/III ratio less than 1800 during the buffer layer deposition process. This mirror surface seems to be the (0 0 0 1)Ga crystallographic face. (C) 1999 Elsevier Science B.V. All rights reserved.