Sharvin resistance and its breakdown observed in long ballistic channels

Abstract
Ballistic transport is studied for relatively narrow channels formed in a high-mobility modulation-doped heterostructure. Sharvin resistance is observed in the constricted channel, whose length is extended to 20 μm as the effective width is decreased to 1.5 μm. This is related to the effect of lateral restriction imposed on the high-mobility structure. We also find a strong reduction of the differential channel resistance at a small applied voltage.