INTERSUBBAND ELECTRON-ELECTRON SCATTERING IN ASYMMETRIC QUANTUM-WELLSDESIGNED FOR FAR-INFRARED EMISSION

Population inversion in inter-subband emitters and lasers depends crit ically on the lifetimes of the nonradiative inter-subband transitions. We find that the often neglected Auger-type processes and Pauli exclu sion effects can dominate the electron-electron scattering contributio ns to the total scattering rate. Electron ex change is also considered . In a range of three-level asymmetric quantum-well structures designe d to produce terahertz radiation, we estimate the potential for laser operation for a range of electron densities and temperatures using the population ratio tau(32)/tau(21). We find that predicted population r atios have a strong dependence on the electron-electron scattering rat es, and that Auger processes and Pauli exclusion are of particular imp ortance. In addition, the temperature dependence of the population rat io is significantly altered by the inclusion of electron-electron scat tering processes. Our results indicate that the interplay of electron- phonon and electron-electron scattering rates suggest optimum operatin g temperatures for different emitter frequencies.