Deep defects in undoped c- and a-plane GaN layers grown by MOVPE onto sapphire substrates were investigated using photoluminescence, photocurrent and thermally stimulated current spectroscopic methods. In a-plane GaN, the photoluminescence spectra were dominated by basal stacking faults and donor–acceptor pair recombination correlated signals, whereas the near band-edge emission was predominant in c-plane GaN layers. In the thermally stimulated current data, no evidence was found for strong trap emission of a-plane GaN correlated with the basal stacking fault-related photoluminescence signal. However, the high concentration of stacking faults in a-plane GaN layers introduced a high concentration of deep defects with activation energies of 220 and 320meV; causing a DAP transition in Pl, a broad peak B in the photocurrent data and thermally stimulated current trap emissions in the temperature range T2. The trap at 220meV was well known in c-plane GaN and was related to dislocations. This supported the assumption that this deep trap was introduced by stacking faults in a-plane GaN.

Characterization of Defects in Undoped Non c-Plane and High Resistance GaN Layers Dominated by Stacking Faults. H.Witte, K.M.Guenther, M.Wieneke, J.Blaesing, A.Dadgar, A.Krost: Physica B, 2009, 404[23-24], 4922-4