FORMATION AND CHARACTERIZATION OF GAAS/AS SUPERLATTICE GROWN BY MOLECULAR-BEAM EPITAXY AT LOW SUBSTRATE-TEMPERATURE

High-resolution X-ray diffractometer and transmission electron microscope (TEM) are used to characterize the redistribution of As precipitates in Si delta-doped GaAs grown by molecular beam epitaxy at low substrate temperature (230 degrees C). The superlattice satellite peaks are observed for samples annealed at 700-800 degrees C for 10 min, which is attributed to the formation of a GaAs/As superlattice during the annealing period. The degree of As precipitates confined on the delta-doped planes is revealed on the intensity of satellite peaks in the X-ray rocking curves, as confirmed by the TEM observations. The lattice expansion and contraction of the annealed low-temperature epitaxial layers can be easily observed from the asymmetry of the satellite peaks.