Excess reverse-bias leakage in GaN films grown by molecular beam epitaxy on GaN templates was correlated with the presence of pure screw dislocations. A scanning current–voltage microscope was used to map the spatial locations of leakage current on high quality GaN films under reverse bias. Two samples with similar total dislocation density (about 109/cm2) but with pure screw dislocation density differing by an order of magnitude were compared. It was found that the density of reverse-bias leakage spots correlated well with pure screw dislocation density, but not with the mixed dislocation density. Thus, pure screw dislocations had a much more detrimental effect upon gate leakage than did edge or mixed dislocations.

Direct Imaging of Reverse-Bias Leakage through Pure Screw Dislocations in GaN Films Grown by Molecular Beam Epitaxy on GaN Templates. J.W.P.Hsu, M.J.Manfra, R.J.Molnar, B.Heying, J.S.Speck: Applied Physics Letters, 2002, 81[1], 79-81