Scanning tunnelling microscopy was used in situ in order to study threading dislocation terminations at the surface of GaN which had been grown, using molecular beam epitaxy, onto a Si(111) surface. The associated surface depressions were imaged at the nm-scale; thus furnishing new insights into the relationship between growth kinetics and dislocation-related surface morphologies. Pure edge dislocations, and ones with a screw component, were easily differentiated and their densities determined. Pure edge dislocations were located at the boundaries of sub-grains which were slightly misoriented in the surface plane. Direct measurements of the spacings of these dislocations yielded the sub-grain misorientation.

In Situ Imaging of Threading Dislocation Terminations at the Surface of GaN(0001) Epitaxially Grown on Si(111) S.Vézian, J.Massies, F.Semond, N.Grandjean, P.Vennéguès: Physical Review B, 2000, 61[11], 7618-21