COMPENSATION EFFECTS IN MG-DOPED GAN EPILAYERS

The compensation of Mg-doped GaN is systematically studied by low-temp erature photoluminescence (PL) using a series of samples with differen t Mg concentrations. Strongly doped samples are found to be highly com pensated in electrical measurements. The compensation mechanism is dir ectly related to the incorporation of Mg. Three different deep donor l evels are found at 240 +/- 30, 350 +/- 30 and 850 +/- 30 meV from the conduction band. With increasing excitation density in photoluminescen ce measurements these levels are subsequently neutralized giving rise to a Jeep unstructured donor-acceptor pair (DAP) emission. These emiss ions exhibit a blueshift that saturates at higher densities, thus excl uding band fluctuations as the prime mechanism for the low energy of t he observed DAP bands. (C) 1998 Elsevier Science B.V. All rights reser ved.