Imaging of friedel oscillation patterns of two-dimensionally accumulated electrons at epitaxially grown InAs(111)A surfaces

Low-temperature scanning tunneling microscopy described the local density of states (LDOS) at the molecular beam epitaxial grown InAs surface on a GaAs(111)A substrate. Standing wave phenomena were continuously observed when the dI/dV mapping was done simultaneously with topography in the conduction band and the LDOS waves were imaged at point defects and within nanostructures. A nonparabolic dispersion relation for the conduction band was observed when the wavelength was measured as a function of bias voltage. The wave features came from the Friedel oscillations of the two-dimensional electron gas in the semiconductor surface accumulation layer.