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. The carrier densities and effective masses were measured by the study of cyclotron resonance using wavelengths in the region 10.6-3.39 mum. This 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 region of 50-60 T, while for (111)A-oriented samples the uncrossing field 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 function of both photon energy and superlattice period, were found to be in good agreement with the predictions of k.p theory.