Hopping energy and percolation-type transport in p-GaAs low densities near the 2D metal–insulator transition at zero magnetic field Review Article

We investigated the temperature dependence of resistivity of a high mobility two-dimensional holes system grown on the (311) GaAs surface in the absence of the magnetic field near the metal–insulator transition. The Coulomb hopping was found in a wide range of temperature and carrier density. Quantitative analysis of our results suggests that a crossover from Efros–Shklovskii to Mott variable range hopping due to screening phenomenon when the hopping distance increases. We found that using the 2D single particle hopping amplitude CES gives unreasonably high localization lengths. Therefore, we believe that electrical transport is dominated by correlated hopping and the hopping amplitude must be renormalized by a reduction factor A≈1.6. The localization length appears to diverge in a power-law fashion near the transition point. The analysis of the hopping gives results consistent with the prediction of the critical point from a recent study of percolation and other experiences.