Optical probing of the minigap in InAs/GaSb superlattices

We report strong modulations in the far infrared absorption of InAs/GaSb se mimetallic superlattices under the influence of a parallel magnetic field a nd attribute this to direct transitions across the minigap. The experiments have been performed on a variety of structures with the measured minigap e nergies in the range 3-23 meV. For narrow layered samples where the two ban d picture is valid a broad minigap absorption is observed. On increasing th e well and barrier widths the absorption decreases in energy and also becom es more localized as more bands anticross to form multiple minigaps. The re sults are compared with parallel field magnetoresistance experiments as wel l as eight band k.p theory.