The properties of C-doped epilayers which had been grown by means of molecular beam epitaxy were studied by using temperature-dependent resistivity, Hall effect measurements, X-ray diffraction and photoluminescence spectroscopy. Doping with C was found to make the layers highly resistive and to quench the band-edge excitonic emissions. A yellow luminescence was still present in C-doped layers. The highly resistive state was attributed to direct compensation by C acceptors and to a resultant enhanced potential barrier at the sub-grain boundaries. Evidence that dislocations joined so as to form potential barriers along the sub-grain boundaries was found in photo-assisted wet-etching experiments on electrically conducting layers.

Properties of Carbon-Doped GaN. H.Tang, J.B.Webb, J.A.Bardwell, S., J.Salzman, C.Uzan-Saguy: Applied Physics Letters, 2001, 78[6], 757-9