SHUBNIKOV-DEHAAS OSCILLATIONS AND QUANTUM HALL-EFFECT IN MODULATION-DOPED HGTE-CDTE SUPERLATTICES

We have investigated quantum oscillations in the magneto-transport properties of HgTe-CdTe superlattices grown by molecular-beam epitaxy. Modulation doping was achieved by incorporating either indium donors or arsenic acceptors into the CdTe barriers. In a p-type sample, quantized plateaus were observed in the Hall conductivity down to i = 3 conduction channels. Since the structure contained 200 periods, this implies that the quantized holes populated only a small fraction of the total superlattice volume. A mixed conduction analysis of the nonoscillating component of magneto-transport data provided confirming evidence for the presence of a two-dimensional hole gas with the appropriate density in addition to the superlattice holes. Previous reports of the quantum Hall effect in HgTe-CdTe also yielded i far less than the total number of superlattice wells. In contrast, an n-type sample from the present study displayed a single quantum Hall plateau at i almost-equal-to 140, indicating that in this case most of the 200 superlattice periods contributed to the conduction. We argue that this represents the first observation of the quantum Hall effect associated with carriers distributed throughout the interior of a HgTe-CdTe superlattice.