Microtwin formation in gallium arsenide by iron ion implantation and amorphization by annealing

Cross-sectional views of iron ion-implanted gallium arsenide to doses of 4×1014 cm−2 and 1×1015 cm−2 were observed by transmission electron microscopy before and after annealing at 673 K. Microtwins were formed below the surface by implantation of 4×1014 ions cm−2. In the sample implanted to the dose of 1×1015 cm−2 , the region below the surface was amorphized and a thin microtwin layer was observed between the amorphous layer and the crystalline matrix. The electron diffraction pattern and the high-resolution multibeam lattice image showed that the structure of the microtwin is an atomic stacking of ABCA″CB″ABC along the 〈111〉 direction. In both samples, the microtwin layer transformed to the amorphous structure by annealing at 673 K for 30 min. It is suggested that the behavior in gallium arsenide implanted with iron, which is much different from that implanted with the other ion species, may be attributed to the coordination number of the covalent bonding iron.