Orateur
Description
Electrical transport on the insulating side of the two-dimensional superconductor-insulator transition (2DSIT) remains nontrivial. Unlike conventional disordered insulators, which exhibit Mott’s variable-range hopping (VRH), insulating films near the 2DSIT display simple activated transport at low temperatures, an activation energy that increases below a characteristic temperature and a voltage-induced breakdown accompanied by large hysteretic jumps in current. Several models, including effective granularity, residual superconductivity, Coulomb-glass physics, electron heating, and collective transport, have been proposed to explain these observations. However, no consensus has emerged. We measure semiconductor n-InSb thin films grown by Molecular beam epitaxy and disordered using controlled exposure to a Ne ion beam. We observe that disordered semiconductors also exhibits many of the same phenomena observed close to the 2DSIT including simple activation, a temperature dependent activation energy and a voltage induced breakdown. By fitting to the linear field enhanced hopping model we extract the average hopping length of the samples. The magnitude of the average hopping length is consistent with hopping between nearest pseudo-grains, thereby supporting the effective granularity picture of transport on the insulating side of the 2DSIT.