Mechanism of ellipsometry monolayer oscillations during metalorganic vapor-phase epitaxy

Ellipsometry signal oscillations were clearly seen during metalorganic vapo r-phase epitaxy (MOVPE) of III-V materials under high sample rotation at 14 00 rpm. The ellipsometric signal oscillated at a period corresponding to 1 ML of MOVPE growth. Oscillations correlated with the formation of islands d ue to nucleation on terraces during the growth of 1 ML. Different surface r econstructions between (100) terraces (As stable) and (111)A step edges (Ga stable) result in different dielectric functions. The effective medium die lectric response of rough and smooth surfaces appears to be responsible for different ellipsometry signals. Layer thickness and InGaAs composition wer e precisely determined in situ. Critical layer thickness and In composition for InGaAs quantum-dot formation were also evaluated directly from in situ ellipsometry data. (C) 2000 American Institute of Physics. [S0021-8979(00) 00113-4].