Thickness-dependent valence-band photoemission from thin InAs and GaAs films

With the aim to follow the development of the electronic properties in thin films, angle-resolved photoelectron spectroscopy has been used to investigate molecular beam epitaxy grown InAs layers on $\mathrm{GaAs}\mathrm{}\left(111\right)A$ and GaAs layers on AlAs(100), lattice mismatch 7.2% and 0.1%, respectively. The results show that the bulk electronic structure in the overlayer material is established only in films thicker than 3–4 nm and that the interface region in effect displays alloylike electronic properties even though the interface is geometrically abrupt. Comparing computations of strain effects on the electronic structure in bulk InAs with the experimental data on the InAs cap layers, it was possible to separate the contributions of geometrical strain effects, extending 5–6 nm into the overlayer, and the electronic interface effects, extending 3–4 nm.