Interface phonons in asymmetric quantum well structures

semiconductor microstructures with many layers, the phonon modes change fro m their bulk form and split into 'confined LO phonons' (LC) and 'interface phonons' (TF), the number and variety of which depends on both the number o f layers and the number of different materials in the structure. This affec ts the electron-phonon scattering rates. Because of the current interest in inter-subband THz emitters, we use these LC and IF modes to evaluate the i nter-subband electron-phonon scattering rate in THz emitter prototypes that are based on four-subband stepped quantum wells. These scattering rates in turn affect the population inversion predicted for these devices, so we co mpare the predicted population inversions for the most promising prototypes against those obtained using bulk phonon scattering rates. (C) 1999 Academ ic Press.