Nonohmic Conductivity as a Probe of Crossover from Diffusion to Hopping in Two Dimensions

We show that the study of nonlinearity conductivity gives a possibility to determine the condition when the diffusion conductivity changes to the hopping one with increasing disorder. It is experimentally shown that the conductivity of single quantum well GaAs/InGaAs/GaAs heterostructures behaves like diffusive one down to the value approaching (2-3) × 10-2e2/h. © 2004 Elsevier B.V. All rights reserved.This work was supported in part by the RFBR through Grants No. 03-02-16150 and No. 04-02-16626, the INTAS through Grant No. 1B290, the CRDF through Grants No. EK-005-X1 and No. Y1-P-05-11, and the Russian Ministry of Education through Grant No. A03-2.9-521