PHOTOLUMINESCENCE SPECTROSCOPY OF MG-DOPED GAN

We have grown Mg-doped GaN films by metalorganic chemical vapor deposi tion with various CP2Mg flow rates. After 750 degrees C postgrowth ann ealing, p-type GaN films with carrier concentrations and mobilities ab out 2 X 10(17)/cm(3) and 10 cm(2)/V s, respectively, have been achieve d. A dominant photoluminescence (PL) line around 2.9 eV was observed a t room temperature. By studying the dependence of PL on excitation den sity at 20 K, the emission line around 2.95 eV can be attributed to a donor-to-acceptor pair transition rather than to a conduction band-to- impurity transition involving the Mg-related deep level. We suggest th at the DAP transition line is caused by a Mg related deep level at abo ut 510 meV above the valence band. It is much deeper than the acceptor level at 250 meV commonly produced by the Mg dopants. (C) 1998 Americ an Institute of Physics. [S0021-8979(98)02720-0]