INSULATOR-LIKE MINIBAND TRANSPORT IN HEAVILY DOPED SUPERLATTICES UNDER HIGH MAGNETIC-FIELDS

We have studied the miniband transport of electrons in heavily doped superlattices under high magnetic fields to examine the possibility of realizing an insulator-like state where all the states in the lowest miniband are completely occupied. A quite large peak is indeed found in the longitudinal magnetoresistance at a magnetic field where the quantum limit is reached, reflecting the presence of a true minigap separating two minibands. The temperature dependence of the peaked feature is also studied to evaluate both the broadening factor and true shape of the density of states.