2-DIMENSIONAL ARSENIC PRECIPITATION IN SUPERLATTICE STRUCTURES OF ALTERNATELY UNDOPED AND HEAVILY BE-DOPED GAAS GROWN BY LOW-TEMPERATURE MOLECULAR-BEAM EPITAXY

The precipitation of arsenic in superlattice structures of alternately undoped and [Be]=2.4 x 10(19) cm(-3) doped GaAs grown at low temperat ures has been studied using transmission electron microscopy. Novel pr ecipitate microstructures were observed in annealed samples, including preferential accumulation of precipitates toward each interface of Be -doped GaAs and the following grown undoped GaAs. Specifically, after 800 degrees C annealing, the precipitates are totally confined in Be-d oped regions, forming mio-dimensional dot arrays near the aforemention ed interfaces. Data are also presented to show that the heavily Be-dop ed GaAs has a smaller lattice constant than the undoped GaAs. A strain -induced mechanism was proposed to account for the segregation of As c lusters. (C) 1998 American Institute of Physics.