RADIATION-PATTERNS OF ACOUSTIC PHONONS EMITTED BY HOT-ELECTRONS IN A QUANTUM-WELL

The acoustic phonon radiation patterns and acoustic phonon spectra due to electron-acoustic-phonon interaction in a double barrier quantum w ell have been investigated by solving both the kinetic equations for e lectrons and phonons. The acoustic phonon radiation patterns have stro ngly pronounced maximum in the directions close to the perpendicular t o the quantum well direction. The radiation pattern anisotropy is expl ained in terms of possible electron transitions, electron distribution function, and the Hamiltonian of electron-phonon interaction. It was shown that, the simple assumption that emitted phonons always have a p erpendicular wave-vector component of the order of 2 pi/a, where a is the width of the quantum well, cannot explain the strong anisotropy of the radiation patterns. More detailed analysis is required and has be en carried out. The emitted acoustic phonon spectra have maxima at ene rgies 2 pi HBARu/a, where u is the sound velocity. (C) 1996 American I nstitute of Physics.