Formation mechanism of Al-segregated region in InAlAs/(110)InP

We studied the formation mechanism of Al-segregated regions in InAlAs/(1 1 0) InP by transmission electron microscopy (TEM). It is found that the Al-s egregated regions observed as dark bands in the TEM image thread upward at certain intervals. The intervals of the regions agree well with the spaces estimated from the distances between one-monolayer steps (1-MLSs) on the su bstrate surface. This suggests that the 1-MLSs play an important role for n ucleation of the Al-segregated region. Based on this finding, we also propo se a model for the nucleation mechanism. (C) 2001 Elsevier Science B.V. All rights reserved.