An investigation into the origin of the 3.424 eV peak in the low-temperature photoluminescence of GaN grown by molecular beam epitaxy

GaN films grown by RF plasma source molecular beam epitaxy (MBE) were inves tigated by low-temperature photoluminescence (PL) and secondary ion mass sp ectroscopy (SIMS). A peak that is generally accepted as being the donor bou nd exciton was observed in all spectra. The energy of the transition varied from sample to sample, but was always in the range of 3.466-3.473 eV. In s ome of the samples, an additional peak was observed. The energy of the tran sition also varied and was in the range of 3.417-3.428 eV. An attempt was m ade to correlate the presence of this peak to the oxygen and silicon conten t of the samples using SIMS. We conclude that, contrary to some previous re ports, the peak seen in the 4K PL spectra of GaN in the region of 3.524 eV cannot always be attributed to oxygen in the film. We also find no correlat ion between the line and the Si or C concentrations. The position of the (D X)-X-0 peak was also found to be independent of the Si and C concentrations .