Enhanced N incorporation and improved optical properties in GaAsN epilayers by using high-index GaAs substrates

GaAsN expilayers were grown on (100), (211)A/B, (311)A/B and (511)A/B GaAs substrates at different temperatures by using a chemical beam epitaxy system. Results of high resolution X-ray diffraction, low- and room-temperature photoluminescence (PL) measurements indicated that dangling bond status (polarity and density) on the growing surface has significant influence on the final N composition and the PL emission behavior in GaAsN epilayers. As compared with the (100) substrate, (n11)B substrates tended to enhance the N incorporation, whereas (n11)A dramatically reduced it. At the growth temperature of 460°C, N composition in (211)B GaAsN is almost 10 times higher than that in (211)A. The extent of enhancement (or reduction) of N incorporation was found to depend on the relative amount of (111)B (or (111)A) component on the growth surface. PL spectra of samples grown at 460°C suggested that optical properties could be improved by most of the adopted (n11) substrates. Especially, efficient N incorporation in GaAsN epilayers can be achieved on (211)B and (311)B substrates while keeping improved crystal quality.