Novel Contrast Mechanism in Cross-Sectional Scanning Tunneling Microscopy of GaSb/GaAs Type-II Nanostructures

Cross-sectional scanning tunneling microscopy results on GaSb quantum wells and dots in GaAs are found to exhibit a narrow, sharply defined contrast of the nanostructure at negative sample bias, but a smoothly broadened contrast at positive sample bias. This contrast is related to the specific type-II band alignment of GaSb/GaAs heterostructures in combination with tip-induced band bending. The corresponding model is quantitatively verified by numerical simulations of band bending and tunnel current profiles combined with calculations of cleavage-induced strain relaxation.