Intrawell and interwell intersubband transitions in multiple quantum wells for far-infrared sources

A theoretical study of electrically pumped unipolar lasers exploiting intrawell or interwell intersubband radiative transitions in multiple quantum-well heterostructures for the generation of IR and FIR radiation is presented. The feasibility of these coherent sources critically depends on the non-radiative intersubband transition rates. Numerical simulations of acoustical phonon, optical-phonon, and electron-electron scattering were implemented, including their temperature dependence. For far-infrared coherent sources, electron-electron scattering emerges as the dominating non-radiative relaxation mechanism. Interwell schemes offer distinctive advantages such as simplicity in design, greater tolerance in design and fabrication errors, field tunability of the emission frequency, improved internal quantum efficiency and aid in establishing population inversion. Design rules are put forward for such long wavelength sources. (C) 1996 American Institute of Physics.