The properties of semi-insulating thick films of Zn-doped GaN grown by hydride vapor phase epitaxy were studied by using cathodoluminescence, transmission electron microscopy and electron holography techniques. The depletion region in the vicinity of threading dislocations was mapped, and it was shown that it was associated with sharp drops in cathodoluminescence intensity. The monochromatic cathodoluminescence images showed considerable intensity variations across the sample surface. These long-range variations in luminescence intensity were also found to be related to potential fluctuations in the regions between dislocations. Such variations could be due to surface states caused by polarization effects of dislocations and/or various surface treatments.

Luminescence Properties of Charged Dislocations in Semi-Insulating GaN:Zn. S.Srinivasan, J.Cai, O.Contreras, F.A.Ponce, D.C.Look, R.J.Molnar: Physica Status Solidi C, 2003, 0[1], 508-11