ELECTRON-INTERFACE PHONON INTERACTION IN MULTIPLE-QUANTUM-WELL STRUCTURES

Intersubband relaxation rates due to electron interactions with the in terface phonons are evaluated for multiple quantum well structures des igned for step quantum well lasers operating at mid-infrared to submil limetre wavelengths. The interface phonon modes and electron-phonon in teraction Hamiltonians for the structures are derived using the transf er matrix method, based on the macroscopic dielectric continuum model, whereas the electron wavefunctions are obtained by solving the Schrod inger equation. Fermi's golden rule is employed to calculate the elect ron relaxation rates between the subbands in these structures. The rel axation rates for two different structures are examined and compared w ith those calculated using the bulk phonon modes and the Frohlich inte raction Hamiltonian. The sum rule for the relationship between the for m factors of the various localized phonon modes and the bulk phonon mo des is verified. The results obtained in this work illustrate that the transfer matrix method provides a convenient way for deriving the pro perties of the interface phonon modes in different structures of curre nt interest and that, for preferential electron relaxation in intersub band laser structures, the effects of the interface phonon modes are s ignificant and should be considered for optimal design of these laser structures.