Effect of indium replacement by gallium on the energy gaps of InAs/GaAs thin-layer structures

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Abstract
Energy gaps of InAs/GaAs thin-layer structures are calculated using a modified finite square well model, which takes into account In-Ga replacement during growth. We compare the calculated results with the experimental energy gaps of structures grown by flow-rate modulation epitaxy, which is based on an alternate supply of gaseous sources, and molecular-beam epitaxy. The results indicate that In-Ga replacement is rare in flow-rate modulation epitaxy, but about 90% of the surface In atoms are replaced with the Ga atoms in molecular-beam epitaxy. Arsenic has a low sticking coefficient on the In surface, so it is difficult to achieve high As coverages on the In surface in molecular-beam epitaxy. In flow-rate modulation epitaxy and metalorganic chemical vapor deposition, the dangling bonds of the surface As atoms are probably terminated by hydrogen atoms. The surface As atoms are stabilized by establishing stable sp3 orbitals and prevent In-Ga replacement.