Size-dependent giant-magnetoresistance in millimeter scale GaAs/AlGaAs 2D electron devices*

This study examines a ``bell-shape'' negative Giant Magneto-Resistance (GMR) that grows in magnitude with decreasing temperatures in $mm$-wide devices fabricated from the high-mobility GaAs/AlGaAs 2-Dimensional Electron System (2DES). Experiments show that the span of this magnetoresistance on the magnetic-field-axis increases with decreasing device width, $W$, while there is no concurrent Hall resistance, $R_{xy}$, correction. A multi-conduction model, including negative diagonal-conductivity, and non-vanishing off-diagonal conductivity, reproduces experimental observations. The results suggest that boundary scattering in the $mm$-wide 2DES with $mm$-scale electron mean-free-paths might be responsible for the observed ``non-ohmic'' size-dependent negative GMR [1]\\[4pt] [1] R. G. Mani, A. Kriisa, and W. Wegscheider, Sci. Rep. 3, 2747 (2013).