MBE growth of different hexagonal GaN crystal structures on vicinal (100) GaAs substrates

GaN thin films of different hexagonal crystal structures have been grown by radio-frequency nitrogen plasma source molecular beam epitaxy (RFMBE) on vicinal (100) GaAs substrates. Polycrystalline hexagonal material occurred for high temperature (630 degreesC) nitridation of the GaAs surface or low temperatures of the initial GaN buffer layer deposition. On the contrary, initial GaN growth at 540 degreesC gave hexagonal single crystals with [0001] axis either inclined at approximately 43 degrees from the growth axis or aligned parallel to it. The GaN orientation depended on the annealing or not, respectively, of the initial low temperature buffer layer. (C) 2001 Elsevier Science B.V. All rights reserved.