AlGaN/AlN-based Quantum Cascade Lasers for mid-IR applications

Quantum Cascade Lasers (QCLs) utilize transitions between sub-bands in the conduction or valence bands to generate coherent light from infrared down lo THz frequencies. Unlike conventional laser diodes (LDs), QCLs are unipolar devices where the emitted light is determined primarily by the device design, i.e., layer thickness and composition, rather than material properties. As such, it is possible to tune the emission of QCLs over a wide range within the same materials system. In addition, since the same electron can emit light .several times by tunneling to the next quantum well in the cascade, these devices can have quantum efficiency greater than one and potentially higher output power than conventional LDs. Herein, we propose to develop QCLs using high-aluminum-content AIGaN and AIN layers, which offer a band offset of ~1.8 eV and with that a wide tunability range. The QCL structures will be grown on native AIN substrates offering low dislocation density, growth of uniform AIGaN alloys and interface control on the monolayer scale. These are all necessary technological ingredients that we have demonstrated over the past few years.