THICKNESS-DEPENDENT ELECTRON ACCUMULATION IN INAS THIN FILMS ON GAAS(111)A: A SCANNING-TUNNELING-SPECTROSCOPY STUDY

Scanning tunneling spectroscopy has been used to study quantum size effects on the electronic structure of thin InAs films grown on $\mathrm{GaAs}(111)A$ substrates, an example of a heterostructure with a relatively large lattice mismatch. The band gap of the InAs films, as measured from current-voltage curves, decreases gradually with film thickness, and electron accumulation occurs in layers that are thicker than 6 nm. Self-consistent calculations suggest the thickness-dependent accumulation is due to quantum size effects and Fermi-level pinning caused by the dislocation network at the InAs/GaAs interface.