HIGH-CURRENT BALLISTIC TRANSPORT THROUGH VARIABLE-WIDTH CONSTRICTIONS IN A HIGH-MOBILITY 2-DIMENSIONAL ELECTRON-GAS

The nonlinear variation of resistance with current for short constrictions in a two-dimensional electron gas has been experimentally established for currents up to 100 A. The nonlinear device characteristics persist over a wide range of constriction widths and thus are not related to quantized conductance effects. At low currents (15 ), a significant decrease in the resistance is observed with respect to the zero-current value, contrary to the expectation that increased electron scattering should lead to a resistance rise. This is attributed to the lowering of a potential barrier in the constriction by the applied bias, leading to an increase in the effective conducting width. An analytical expression for this low-current phenomenon is derived and is shown to give reasonable agreement with the experimental observations. © 1995 The American Physical Society.