The impact of the Ga adlayer coverage on the surface morphologies and pit densities of GaN (00▪1) films grown by plasma-assisted molecular beam epitaxy was studied by using quantitative in situ quadrupole mass spectrometry. As the equilibrium Ga adlayer coverages rise continuously from 0 to 2.5 monolayers the surface pit densities decreased from about 2 x 109/cm2 to zero, yielding characteristic step-flow and spiral growth hillock features. These results showed that there was a direct and quantitative link between Ga adlayer coverage, adatom diffusion and surface defect structure without any discontinuities.

Ga Adlayer Governed Surface Defect Evolution of (0001)GaN Films Grown by Plasma-Assisted Molecular Beam Epitaxy. G.Koblmüller, J.Brown, R.Averbeck, H.Riechert, P.Pongratz, J.S.Speck: Japanese Journal of Applied Physics, 2005, 44[28], L906-8