Effects of rapid thermal annealing and SiO_(2) encapsulation on GaNAs/GaAs single quantum wells grown by plasma-assisted molecular-beam epitaxy

摘要

Effects of rapid thermal annealing and SiO_(2) encapsulation on GaNAs/GaAs single quantum wells grown by plasma-assisted molecular-beam epitaxy were studied. Photoluminescence measurements on a series of samples with different well widths and N compositions were used to evaluate the effects. The intermixing of GaNAs and GaAs layers was clearly enhanced by the presence of a SiO_(2)-cap layer. However, it was strongly dependent on the N composition. After annealing at 900℃ for 30 s, a blueshift up to 62 meV was observed for the SiO_(2)-capped region of the sample with N composition of 1.5, whereas only a small blueshift of 26 meV was exhibited for the bare region. For the sample with the N composition of 3.1, nearly identical photoluminescence peak energy shift for both the SiO_(2)-capped region and the bare region was observed. It is suggested that the enhanced intermixing is mainly dominated by SiO_(2)-capped layer induced defects-assisted diffusion for the sample with smaller N composition, while with increasing N composition, the diffusion assisted by interior defects become predominant.