The initial stage of InGaAs growth by MOVPE on multiatomic-stepped GaAs structures

We investigate the formation of self-organized InGaAs quantum wires (QWRs) on coherent multiatomic-stepped GaAs that had been grown on GaAs vicinal su bstrates by metal-organic vapor phase epitaxy. The key issues in the format ion of InGaAs QWRs are the uniformity of the multiatomic steps and the larg e modulation in the lateral thickness of InGaAs on multiatomic-stepped GaAs structures. We use images obtained by atomic force microscopy and cross-se ctional images of InGaAs layers obtained by transmission electron microscop y to investigate the surface morphology of InGaAs layers on multiatomic-ste pped GaAs structures. As a result, we found that in the initial stages of I nGaAs growth, Ga and In atoms preferentially attach themselves to the botto m edges of the multiatomic steps, and multiatomic-stepped structures with t heir own characteristic period and then reappear. These results suggest tha t the Schwoebel barrier, which causes the step bunching, may be decreased b y the change of surface reconstruction after the introduction of small amou nt of In atoms to GaAs surfaces in the initial stage of growth. Furthermore , multiatomic-stepped structures formed during the growth of InGaAs layers have different periods from those on the underlying GaAs layer. The differe nce between the multiatomic-stepped structures on GaAs and InGaAs is though t to be caused by the difference of Schwoebel barriers between these two st epped surfaces. (C) 2001 Elsevier Science B.V. All rights reserved.