Surface and Subsurface Imaging of Indium in InGaAs by Scanning Tunneling Microscopy

Investigating the ternary In$_{x}$Ga$_{1-x}$As alloy ($x \sim 12\%$) by cross-sectional scanning tunneling microscopy, we find that on the UHV-cleaved (110) surface the In distribution in both the surface and the first subsurface layer can be atomically resolved in the empty- and filled-state images, respectively. This is found to be mostly a geometric effect due to the larger size of the In. We apply this method to study the incorporation of In during the growth of In$_{0.12}$Ga$_{0.88}$As quantum wires on nonplanar substrates. Strong In segregation in the growth direction is seen in the structure, and we compare the incorporation profiles across the quantum wire and a planar quantum well. No In clustering beyond the statistical expectation is observed.