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The precipitation of arsenic in annealed Be delta-doped GaAs grown by low-temperature molecular-beam epitaxy has been studied using transmission electron microscopy. It was found that the planes doped with [Be] = 1.0 10[sup 14] cm[sup -2] always accumulate As precipitates, while the planes doped with [Be] = 1 × 10[sup 13] cm[sup -2] tend to deplete As precipitates. In contrast, the planes doped with [Be] = 3 and 2 × 10[sup 13] cm[sup -2] exhibit a weak accumulation property when annealed at 700 °C, but a depletion property when annealed 800 °C. The existence of twins and/or precipitates around the [Be]= 1.0 × 10[sup 14] cm[sup -2] doped planes found in the as-grown sample suggests a strain-induced mechanism to account for the As precipitates accumulation on these planes. [ABSTRACT FROM AUTHOR]

The precipitation of arsenic in superlattice structures of alternately undoped and [Be]=2.4×10[sup 19] cm[sup -3] doped GaAs grown at low temperatures has been studied using transmission electron microscopy. Novel precipitate 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 °C annealing, the precipitates are totally confined in Be-doped regions, forming two-dimensional dot arrays near the aforementioned interfaces. Data are also presented to show that the heavily Be-doped GaAs has a smaller lattice constant than the undoped GaAs. A strain-induced mechanism was proposed to account for the segregation of As clusters. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]