QUANTUM HALL-EFFECT IN HGTE-CDTE SUPERLATTICES WITH STRONG 3-DIMENSIONAL DISPERSION

We have studied the quantum Hall effect in modulation-doped HgTe-CdTe superlattices with electron concentrations in the range 8 x 10(15) less-than-or-equal-to n less-than-or-equal-to 3 x 10(17) cm-3. Since the quantum Hall phenomenon should in principle be restricted to two-dimensional systems, it is not surprising that the plateaus in the Hall conductivity (at multiples of almost-equal-to 200e2/h in the 200-period superlattices) and minima in the diagonal conductivity are most pronounced in samples with relatively thick barriers, i.e., when the energy bands have little dispersion in the growth direction. However, well-resolved quantum Hall features are also observed in thinner-well superlattices having miniband widths of up to 17 meV. While present phenomenological models can account for this as long as the Landau level spacing is large compared to the miniband width, it is surprising that broad lowest-order plateaus are also evident in data for two superlattices having little or no gap between adjacent levels. Possible implications of this finding are discussed.