RESONANT TUNNELING AND HOPPING THROUGH A SERIES OF LOCALIZED STATES IN A 2-DIMENSIONAL ELECTRON-GAS

We report measurements of the temperature and length dependence of the conductance of a wide two-dimensional electron gas in a strongly localized regime. Our results indicate that the conduction occurs via resonant tunneling below about 0.1 K and, at higher temperatures, via hopping through channels that contain more than one localized state. A dramatic increase of the average logarithm of conductance <InG> with the increasing sample length is observed in the tunneling regime, for which there is no satisfactory theoretical explanation yet. This effect persists even up to greater-than-or-similar-to 4.2 K.