Terahertz (THz) electro-luminescence from AlGaAs-GaAs quantum cascade heterostructures

Summary form only given. Multi-quantum well III-V heterostructure materials have been used for the development of the unipolar quantum cascade (QC) laser operating in the mid-infrared. This scheme is now being extended to the far infrared (1 to 20 THz). The dynamics in this spectroscopic region, however, are very different from those in the mid-infrared. Non-radiative mechanisms (LO phonon and carrier-carrier scattering) need to be considered carefully, as the associated energies are larger or comparable with the THz intersubband emission. Further, blackbody or thermal radiation can conceal the intersubband transition. Difficulties in measurement, such as the lack of fast far-infrared detectors, also present challenges. The paper reports on a series of Al/sub 0.15/Ga/sub 0.85/As-GaAs quantum cascade electroluminescence devices designed to emit in the FIR. Electrical and optical studies were used to characterise the devices, the latter employing a step-scan infrared spectrometer.