Effects of rapid thermal annealing and SiO2 encapsulation on GaNAs/GaAs single quantum wells grown by plasma-assisted molecular-beam epitaxy

Effects of rapid thermal annealing and SiO2 encapsulation on GaNAs/GaAs sin gle quantum wells grown by plasma-assisted molecular-beam epitaxy were stud ied. Photoluminescence measurements on a series of samples with different w ell widths and N compositions were used to evaluate the effects. The interm ixing of GaNAs and GaAs layers was clearly enhanced by the presence of a Si O2-cap layer. However, it was strongly dependent on the N composition. Afte r annealing at 900 degreesC for 30 s, a blueshift up to 62 meV was observed for the SiO2-capped region of the sample with N composition of 1.5%, where as 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 photoluminescen ce peak energy shift for both the SiO2-capped region and the bare region wa s observed. It is suggested that the enhanced intermixing is mainly dominat ed by SiO2-capped layer induced defects-assisted diffusion for the sample w ith smaller N composition, while with increasing N composition, the diffusi on assisted by interior defects become predominant. (C) 2001 American Insti tute of Physics.