Mid-infrared (3-5 /spl mu/m) intersubband electroluminescence in InAs/AlSb quantum cascade structures

Summary form only given. Quantum cascade (QC) lasers have already demonstrated very encouraging results at wavelengths longer than 4 /spl mu/m. In these devices based on intersubband transitions, the highest attainable photon energy is limited by the conduction band offset /spl Delta/E/sub c/. Until now, QC devices have been demonstrated on two material systems: InGaAs/InAlAs/InP and Al/sub x/Ga/sub 1-x/As/GaAs. We propose to extend the concepts of QC lasers to InAs/AlSb heterostructures, grown strain compensated on GaSb. In this material system, the /spl Gamma/-point band discontinuity is very large (/spl Delta/E/sub c//spl cong/2.1 eV) and it is therefore possible to design active regions which cover the 3-5 /spl mu/m atmospheric window. Our QC structures were designed following a diagonal scheme. In this design, the wavefunctions of the upper and lower states of the laser transition are spatially separated. This enables to increase the selectivity of the injection of the electrons into the excited state of the transition and therefore to limit direct injection into the lower state of the active region.