It was recalled that previous studies had shown that reactive ion beam pre-treatment of sapphire, before GaN deposition, resulted in a reduction of the dislocation density in the GaN film. It was also found that an amorphous phase remained at the interface after deposition at high temperatures. Annealing was performed in order to obtain structural changes due to recrystallization of the remaining amorphous phase, and to study their effect upon the electrical properties of GaN thin films on a reactive ion beam-treated sapphire (00•1) substrate. The DCXRD spectra and Hall mobility of the specimens were studied as a function of the annealing time at 1000C in a N atmosphere. In the annealed specimens, the full-width at half-maximum of the DCXRD decreased and the mobility increased. The annealed specimens were compared with non-annealed samples by using transmission electron microscopy. A decrease in lattice strain, and a reduction in dislocation density of 56 to 59%, were observed. The results showed that a combination of reactive ion beam pre-treatment, and suitable annealing, improved the properties of GaN films grown by metalorganic chemical vapour deposition.

Reduction of Defects in GaN on Reactive Ion Beam Treated Sapphire by Annealing. D.Byun, J.Jhin, S.Cho, J.Kim, S.J.Lee, C.H.Hong, G.Kim, W.K.Choi: Physica Status Solidi B, 2001, 228[1], 315-8