Influence of Si doping on the subgrain structure of GaN grown on AlN/Si(111)

Abstract

This work presents a detailed study of the subgrain structure of Si doped GaN grown on AlN buffered (111)Si substrates by plasma-assisted Molecular Beam Epitaxy. Si doping increases from an unintentionally undoped sample up to 1.7×1019 cm-3. The subgrain size distribution fits quite precisely a Gaussian distribution for the undoped sample. The asymmetry and standard deviation of such distribution increases with Si doping. The average subgrain size decreases as the Si doping increases. Its value is 177 nm for a Si doping of 6.0×1018 cm-3 and it increases up to 282 nm for the undoped sample. On the other hand, though the subgrain boundaries appear to be free of any precipitate in the nominally undoped sample, particles of a few nm2 have been observed at the boundaries between the subgrains of the Si doped films.