By using gas-source molecular beam epitaxy, with NH3 as a N source, an investigation was made of the effect of buffer-layer preparation upon the properties of epilayers. It was found that the buffer-layer thickness and buffer annealing time had a marked effect upon the Hall mobility and the background carrier density of the layers. In an optimized buffer layer, a mobility of about 190cm2/Vs was achieved and was correlated with defect densities as low as 2.1 x 109/cm2. The variation in the intensity of defect-related lines in photoluminescence spectra was used to confirm a decrease in the defect density with increasing mobility.

Effect of Buffer Layer Preparation on GaN Epilayers Grown by Gas-Source Molecular-Beam Epitaxy. V.Bousquet, J.Heffernan, J.Barnes, S.Hooper: Applied Physics Letters, 2001, 78[6], 754-6