Magnetoquantum oscillations of the Hall coefficient RH were observed in Te-doped GaSb layers grown by molecular beam epitaxy. The free electron densities were in the low 1016 cm-3 range or even slightly lower, thus achieving, for the first time in GaSb, the extreme quantum limit, where all the electrons occupy the spin-split 0(+) Landau level (LL). Similarly to other known cases, the amplitude of the last maximum of RH could be explained as enhanced by the metal-to-insulator transition of the spin-down electron system in the n=0 LL. The occurrence of the last negative oscillation of RH below its classical value, called Hall dip, could be frustrated, in samples with sufficiently low carrier densities, by an incipient carrier freeze-out at donor impurities induced by the magnetic field.
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