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

This work presents a detailed study of the subgrain structure of Si doped G aN grown on AIN buffered (111)Si substrates by plasma-assisted Molecular Be am Epitaxy. Si doping increases from an unintentionally undoped sample up t o 1.7 x 10(19) 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 subgra in size decreases as the Si doping increases. Its value is 177 nm for a Si doping of 6.0 x 10(18) cm(-3) and it increases up to 282 nm for the undoped sample. On the other hand, though the subgrain boundaries appear to be fre e of any precipitate in the nominally undoped sample, particles of a few nm (2) have been observed at the boundaries between the subgrains of the Si do ped films.