STM STUDIES ON QUANTUM-WIRE STRUCTURES IN AIR AND LIQUID-HELIUM

In this work, low temperature scanning tunneling microscopy (STM) stud ies on quantum wires are reported, which were fabricated by laser holo graphy and wet chemical etching. Inverted heterostructures with thin a nd highly doped cap layers were used as substrates in order to keep th e total tunneling barrier as small as possible. Current-voltage curves were measured on the wires and in the depleted areas between them. Be tween the wires, significant current is only observed for electrons wh ich tunnel from the GaAs valence band into the STM tip, whereas symmet ric current-voltage curves are observed on the wires. This behavior is ascribed to the influence of surface depletion and thus, a comparison of current imaging spectroscopy data taken at 300 K and in liquid hel ium directly yields the edge depletion width of the quantum wires. (C) 1996 Academic Press Limited