Magneto-oscillations of the Hall coefficient in n-type GaSb at the extreme quantum limit

Magnetoquantum oscillations of the Hall coefficient R_H 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 R_H 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 R_H 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.