Scaling of the breakdown in the impurity band of doped GaAs/AlGaAs quantum well demonstrating virtual Anderson transition

We observed breakdown behavior for highly doped and low compensated p-type layers located within the central part of GaAs/AlGaAs quantum wells at rather small values of the applied bias. This behavior is attributed to the presence of the band of extended states (BES) within the impurity band. Namely, we believe that the breakdown is due to impact ionization of the carriers from the Fermi level to BES while the fact that the highly conducting state is supported at lower voltages than the threshold ones is explained by detrapping of the carriers captured from the BES to intermediate localized levels. A special attention was paid to the temperature behavior of the threshold voltages as functions of the current as well as of the voltages corresponding to highly conducting state. It appeared that these voltages are independent of the current and are controlled exclusively by the properties of the sample. To our opinion, it gives a strong evidence of the validity of our model.