Growth Processes of GaAs Grown by Atomic Layer Epitaxy Revealed by Atomic Force Microscopy

Abstract
The growth processes of GaAs grown by atomic layer epitaxy (ALE) are examined on an atomic scale using atomic force microscopy (AFM). The examination reveals that two-dimensional (2-D) nucleation and step-propagation growth take place simultaneously under ALE growth conditions. The critical terrace width below which only step-propagation growth occurs is 300–600 nm in spite of the low growth temperature. This is two to three orders of magnitude larger than the values for molecular beam epitaxy and metalorganic chemical vapor deposition extrapolated to the ALE temperature. It is assumed that the migration of the undecomposed TMG on an As-stabilized surface is responsible for the large critical terrace width in ALE.