Reciprocal space x-ray mapping and transmission electron microscopic studies of coincided #delta#-InAs and As-cluster superlattices in GaAs films grown by molecular-beam epitaxy at low temperature

摘要

InAs/GaAs superlattices with thin (0.5-1 monolayer) #delta#-InAs insertions were grown by molecular beam epitaxy at low (150-200deg C) temperature. The as-grown samples contained up to 10~(20) cm~(-3) arsenic antisite defects. Transmission electron microscopic study revealed no extended defect and showed that the real thickness of #delta#-InAs insertions is 3-4 monolayers. This thickness seems to be due to short-range roughness of the growth surface. Low diffuse scattering and extended interference picture were observed for such superlattices by x-ray diffraction study. Superlattices of two-dimensional cluster sheets were produced by annealing of the #delta#-InAs/GaAs superlattices at 500-600 deg C. Precipitation of excess arsenic at InAs #delta#-layers was found to be accompanied by enhanced In-Ga intermixing, roughening the InAs #delta#-layers, and smoothing the x-ray interference picture. No evidence for any self-ordering in the system of nanoscale As clusters was revealed using x-ray mapping in reciprocal space.