A study of annealed GaN grown by molecular beam epitaxy using photoluminescence spectroscopy.

Photoluminescence (PL) spectroscopy has been used to investigate the effect annealing has on molecular beam epitaxially grown GaN in different ambient s. By observing the changes in the PL spectra as a function of ambient temp erature and atmosphere used, important information concerning the origin of defects within GaN has been found. Samples were annealed in different atmo spheres, (including oxygen, oxygen and water vapour, nitrogen and argon), d ifferent temperatures. In the 2.0eV-2.8eV region of the PL spectra, two pea ks appeared at approximately 2.3eV and 2.6eV, somewhat higher than the usua l yellow luminescence peak. We find that the 2.6eV peak is dominant for hig h annealing temperatures and the 2.3eV peak dominates at low annealing temp eratures for the samples annealed in oxygen. When annealed in argon and nit rogen the 2.6eV peak dominates at all annealing temperatures. Changes in th e PL spectra between anneals were also seen in the 3.42eV region. The 3.42e V peak is often assigned to excitons bound to stacking faults. Power resolv ed measurements indicate that in our sample the cause is a donor acceptor p air transition.