TERAHERTZ ACOUSTIC-PHONON SIGNAL GENERATED BY HEATED ELECTRONS IN ALGAAS GAAS-BASED QUANTUM WIRES/

In this paper, we explore theoretically the possibility of applying Al GaAs/GaAs-based quantum wire systems as a terahertz (THz) ultrasonic g enerator. For structures such as AlxGa1-xAs/GaAs-based low-dimensional semiconductor systems and semiconductor nanostructures, electrons are confined within the nanometer distance scale so that energies (e.g. e lectronic subband energy, electron kinetic energy, Fermi energy, etc.) are in the meV scale, which consequently results in the acoustic-phon ons generated by heated electrons from these novel systems to be aroun d the TH2 frequency range. Our theoretical results indicate that: (i) AlxGa-xAs/GaAs-based quantum wires are suitable for generating THz aco ustic-phonon signals; (ii) both longitudinal and transverse acoustic-p honon modes contribute to the detected phonon signals; (iii) the THz u ltrasound wave can be generated through both intra- and inter-subband scattering processes; and (iv) the strong dependence of the acoustic-p honon emission from a quantum wire on phonon frequency and phonon emis sion angle can be observed. (C) 1995 Academic Press Limited