Growth-temperature dependence of the microstructure of ErAs islands in GaAs

This article concerns the growth-temperature dependence of the microstructure of ErAs islands embedded in GaAs. The material was grown by molecular-beam epitaxy. The nucleation of ErAs on GaAs occurs in an island growth mode leading to spontaneous formation of nanometer-sized islands. Multiple layers of ErAs islands separated by GaAs can be stacked on top of each other to form a superlattice along the growth direction. A series of four such samples were grown at growth temperatures of 480 degreesC, 535 degreesC, 580 degreesC, and 630 degreesC. For all samples, 1.8 monolayers of ErAs were deposited in each layer of the superlattices. The microstructure of these samples was investigated by x-ray diffraction and transmission electron microscopy. We find that single crystallinity was maintained across the layers of ErAs islands at the growth temperatures of 535 degreesC, 580 degreesC, and 630 degreesC. At the growth temperature of 480 degreesC, however, the sample was not single crystalline. The GaAs matrix of the sample was defective. With increasing growth temperature, the size of the ErAs islands increased and the areal density,of the ErAs islands decreased. The size increase is due to an increasing lateral (in-plane) dimension; the height of the islands is essentially unchanged. (C) 2003 American Vacuum Society.