Shear Acoustic Phonons in Multilayer Arsenide Semiconductor Nanostructures

Using the elastic continuum model, exact analytical solutions for the equations of motion for the elastic medium of a multilayer resonant tunneling nanosystem describing the shear modes of acoustic phonons are obtained. The expressions describing the components of the stress tensor arising in the studied nanostructure and boundary conditions for the components of the elastic displacement vector and the components of the stress tensor are obtained. Using the obtained equations of motion for the elastic medium and boundary conditions, the theory of the spectrum and phonon modes for shear acoustic phonons is developed in the proposed work for a plane arsenide semiconductor nanostructure. It is shown that the spectrum of the displaced acoustic phonons of the studied nanosystem is obtained from the dispersion equation following from the boundary conditions using transfer-matrix method. Using the orthonormality condition, the normalized modes of shear acoustic phonons are obtained. For the parameters of the three-barrier nanostructure – the active zone of a quantum cascade detector – the calculation of the spectrum of acoustic phonons and its dependencies on the wave vector and the geometric parameters of the nanostructure has been performed. It is shown that the calculated dependences of the spectrum of acoustic phonons on the wave vector form three groups with boundary values equal to the corresponding energies of acoustic phonons in massive crystals. Also it is obtained that an increase in the thickness of the internal barrier at constant other geometrical parameters of the nanosystem leads to a steady decrease in the values of the phonon energy levels energies. The proposed theory can be used to study the scattering of electron fluxes on acoustic phonons in multilayer resonant-tunneling structures.Keywords: Acoustic phonons, Phonon modes, Resonant-tunneling structure, Quantum cascade laser, Quantum cascade detector.