Multiband coupling effects on electron quantum well intersubband transitions

We discuss multiband coupling effects on electronic intersubband single particle excitations (SPE) of infrared (IR) and Raman processes in type I quantum wells (QWs). Interband couplings between Γc1-Γv15, Γc1-Γc15, and Γc15-Γv15 bulk band edges are treated within 14-band k⋅p first-order perturbation theory. Enhanced band-mixing effects are observed at Brillouin zone center (k∥=0) because of quantization effects (kz≠0). For zinc-blende-type QWs, Γc15-Γv15 band-mixing effects at high-lying Γc1 conduction subbands contribute (x,y)-polarized IR and z(x,x)z̄- and z(x,y)z̄-polarized Raman intersubband SPE. Intersubband polarization splittings occur when the QWs are under biaxial strains.