Twinning of As precipitates in low-temperature GaAs during high temperature annealing

Twinning of nano-scale As precipitates formed in low-temperature GaAs during high temperature annealing was studied by high resolution electron microscopy. Symmetrical {1~104~} twins were nucleated during crystallization of amorphous or liquid-like As precipitates. Nucleation of rhombohedral As appears to be most favorable on the short facet that is parallel to the {111}B plane of the GaAs. Twin formation then often initiates on the long facet bounded by the {111}A plane. The crystallization front terminates with a void because of the shrinkage of the As volume during solidification.