DOUBLE-BARRIER COHERENT SOUND GENERATOR - A NEW DEVICE

We investigate a new device, a SASER, consisting of a double-barrier h eterostructure (DBH) designed to generate ultra-high-frequency coheren t sound. The device is tailored such that under the influence of an ex ternal bias, some of the electrons injected into the first excited lev el decay to the ground state by emitting LO-phonons. Due to the low en ergy and short wavelength of the phonon beam, this device can be used for imaging, for non-destructive characterization of nanostructures an d to construct phonoelectronic systems (analogous to optoelectronics). In this paper we use a simple model to calculate the electronic curre nt which takes into account the electron-phonon and electron-electron interactions. The electronic part is described in terms of a tight-bin ding Hamiltonian. Lattice dynamics are presented by a single LO-phonon mode confined inside the well for the primary beam and another single TA-phonon mode for the secondary one (F. Vallee, Phys. Rev. B49, 2460 (1994)). The electron-phonon interaction is described by a single tra nsition matrix element between the two lowest states localized at the well. The electron and phonon populations, the current and the potenti al profile are calculated self-consistently. The results confirm the v iability of the device, predicted in previous simplified calculations (S. S. Makler et al., Surf. Sci. 361, 239 (1996)). (C) 1997 Academic P ress Limited.