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 ef fects on the electronic structure of thin InAs films grown on 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 cu rrent-voltage curves, decreases gradually with film thickness, and ele ctron accumulation occurs in layers that are thicker than 6 nm. Self-c onsistent calculations suggest the thickness-dependent accumulation is due to quantum size effects and Fermi-level pinning caused by the dis location network at the InAs/GaAs interface.