Abstract
The structural and optical qualities of superlattice InAs-GaAs structures and quantum dots (QDs), grown by molecular beam epitaxy (MBE) at low (250 degrees C) and normal (similar to 450 degrees C) growth temperatures, have been investigated. The InAs layers (3 monolayers) were grown under conditions where only the indium beam impinged upon the growth surface (surfactant growth mode). This growth mode still resulted in the formation of QDs at normal growth temperatures, but with dot sizes that were much smaller than those for "normal" growth of 3ML InAs-GaAs QD structures. In addition, at low temperature under such "arsenic-free" conditions a very high quality InAs-GaAs superlattice structure with 3 ML of InAs was formed, as demonstrated by transmission electron microscopy (TEM). This is a direct confirmation that the critical thickness of InAs can be extended well beyond the 1.7 ML limit seen at higher growth temperatures. (c) 2008 Elsevier Ltd. All rights reserved.