Self-organized quantum dots have been used with great success in quantum dot infrared photodetectors (QDIPs), wherein intersublevel transitions between confined electron states are utilized. Many attributes make self-organized quantum dots attractive for the realization of intersublevel infrared light sources for the mid- to far-infrared wavelength range. Intersublevel electroluminescence has been demonstrated from both bipolar and quantum cascade unipolar
structures, with coherent emission observed in the bipolar case. Coherent mid-infrared emission from bipolar selforganized quantum dot devices has been observed at room temperature, centered at 13μm. The cavity is designed to support both intersublevel and interband light, so that interband lasing can quickly depopulate the ground state of the quantum dots. Devices show a distinct turn-on at 1.1kA/cm2 but suffer from broad linewidth. Unipolar quantum dot cascade structures are being designed with a strain-compensating GaAs1-xNx / GaAs injector region. Using this material system, structures with as many as 30 cascade periods have been successfully grown by molecular beam epitaxy
(MBE). TE polarized electroluminescence at 22μm has been observed from such structures at cryogenic temperatures.