Intersubband transitions in InAs/GaSb semimetallic superlattices

We report parallel magnetic-field-activated intersubband absorption in InAs/GaSb semimetallic superlattices. The samples were studied in the Voigt configuration enabling normal-incidence excitation of the intersubband transition. For samples with narrow wells, the small absorption coefficient meant that an alternative waveguide configuration was used, again with magnetic field applied parallel to the superlattice layers. In this latter configuration we see further activation of the intersubband resonance by the parallel field as well as new transitions to higher subbands. The intersubband energy and absorption characteristics are studied over a large range of well widths and compared with results from eight-band k·p calculations.