OBSERVATION OF MAGNETIC-FIELD-INDUCED SEMIMETAL-SEMICONDUCTOR TRANSITIONS IN CROSSED-GAP SUPERLATTICES BY CYCLOTRON-RESONANCE

A transition from semimetallic to semiconducting behavior induced by a magnetic field has been observed in type-II superlattices of InAs/Ga1 -xInxSb by the use of very high magnetic fields, in excess of 100 T. T he carrier densities and effective masses were measured by the study o f cyclotron resonance using wavelengths in the region 10.6-3.39 mum. T his was used to demonstrate that the zero-point energy associated with the lowest-electron and highest-hole Landau levels was sufficient to uncross the energy bands in long-period, semimetallic structures. For (100)-oriented structures this transition was found to occur in the re gion of 50-60 T, while for (111)A-oriented samples the uncrossing fiel d was found to move up to the region of 100 T, due to an orientational dependence of the band offset. The effective masses, studied as a fun ction of both photon energy and superlattice period, were found to be in good agreement with the predictions of k.p theory.