Samples of annealed p-type N-doped material that had been prepared by means of molecular beam epitaxy were then characterized by using photoluminescence spectroscopy, capacitance-voltage profiling, and secondary ion mass spectroscopy. It was found that a decrease in active acceptor concentration during annealing arose from compensation by defects that originated from the surface. By fitting the N acceptor profiles with solutions to the diffusion equation, it was estimated that the migration energy of the compensating defect was 4.0eV.

A.L.Chen, W.Walukiewicz, K.Duxstad, E.E.Haller: Applied Physics Letters, 1996, 68[11], 1522-4