Anomalous electron transport in doped uncompensated p-GaAs/AlGaAs quantum wells: evidence of virtual Anderson transition

作者：Agrinskaya N V^*; Galperin Y M; Kozub V I; Shamshur D V

来源：Journal of Physics: Condensed Matter , 2008, 20(39): 395216.

DOI：10.1088/0953-8984/20/39/395216

For highly doped uncompensated p-type layers located within the central part of GaAs/AlGaAs quantum wells, we observed the activated low-temperature behavior of conductivity. The low values of the activation energy, epsilon(4) = (1-3) meV, cannot apparently be ascribed to standard mechanisms. We attribute this behavior to the existence of a narrow band of extended states near the maximum of the density of states in the impurity band. The Hubbard repulsion prevents metallic transport of holes over these states. However, the minority carriers-electrons-supplied by background defects and situated at low temperatures within the tail of the impurity band can be activated to the above mentioned band of extended states. We refer to this behavior as the virtual Anderson transition since the conductance is maintained by the extended states formed within the impurity band though the conductivity is not metallic. The low-temperature (T less than or similar to 4 K) conductance is strongly non-Ohmic: the I-V curves are S-shaped that leads to a breakdown behavior. We explain the observed low threshold fields (less than or similar to 10 V cm(-1)) by the fact that we are dealing with the impact ionization of the electrons from the states below the chemical potential to the band of extended impurity states situated close to the chemical potential, the ionization energy being small.

• 出版日期2008-10-1