INTERSUBBAND RESONANCES IN INAS ALSB QUANTUM-WELLS - SELECTION-RULES,MATRIX-ELEMENTS, AND THE DEPOLARIZATION FIELD/

We present both theoretical and experimental results on the intersubba nd resonance in InAs/AlSb quantum wells. From a Kane (k . p) descripti on of the band structure we investigate the effect of the large nonpar abolicity and of the high Fermi wave vector on the selection rules and matrix elements. The 1-2 transition in parallel excitation (x) is sho wn to be very weak from simple parity arguments; in perpendicular exci tation (z) the matrix element [z] is shown to be largely unaffected by nonparabolicity. The 1-3 transition turns out to be very weak in both geometries. Two band-gap engineering approaches to enhancing the para llel excitation of 1-2 are considered but the effect remains small as compared to the conventional z excitation. In z excitation the depolar ization field condenses all the oscillator strength into essentially o ne sharp line despite the broadening expected from the nonparabolicity in the band dispersions. Inclusion of the depolarization field in the theory gives us good agreement with both the experimentally determine d line shape and [z] matrix element.