PHOTOLUMINESCENCE OF MBE GROWN WURTZITE BE-DOPED GAN

We report new lines in the photoluminescence (PL) spectrum of lightly Be-doped GaN. The low-temperature PL spectrum of the lightly doped sam ple is dominated by a transition at 3.385 eV with first and second LO phonon replicas. Power-resolved PL measurements showed that the peak a t 3.385 eV narrowed in width and shifted to higher energies with incre asing excitation intensity. Thus the transition is attributed to donor -to-acceptor recombination, involving a Be acceptor of optical ionizat ion energy of between 90 and 100 meV, This is much shallower than the acceptor level of 250 meV induced by Mg doping. Increasing the doping, however, resulted in a quenching of the band-edge luminescence and th e appearance of a broad transition centred around 2.4 eV which we assi gn to a complex involving Be. Undulations on the peak were consistent with interference effects. On increasing the doping level even further all luminescence was quenched.