Incorporation of deep defects in GaN induced by doping and implantation processes

Galliumnitride layers grown by molecular beam epitaxy on sapphire and doped with magnesium, calcium, and carbon as possible accepters were investigate d by optical admittance spectroscopy with respect to the existing deep defe cts. While p-type conductivity was achieved by magnesium doping, calcium an d carbon doping did not overcompensate the background n-type conductivity. This phenomenon is explained by the generation of compensating defects, mai nly electron traps and donors. A correlation between the creation of compen sating centers and the flux of the doping element is observed. This doping induced defect introduction is compared with the effect of ion implantation , which generates additional intrinsic defects, These investigations lead t o the conclusion, that the new donors due to carbon doping are nitrogen Vac ancies generating an electronic level at E-C - (53 +/- 8) meV.