DYNAMICAL SIMULATION OF OPTICAL PHONON TRANSFER IN THE GAAS ALXGA1-XAS/GAAS SINGLE-BARRIER STRUCTURE/

Dynamical transfer of optical phonons in the GaAs/AlxGa1-xAs/GaAs sing le-barrier structure is simulated using a classical three-dimensional lattice-dynamics model, fully taking into account the random arrangeme nt of Ga and Al atoms in the alloy barrier. The transmission coefficie nt of GaAs optical phonons through the alloy barrier exhibits, for giv en barrier thickness, an exponential decay with x in the small-x regim e, and remains at a small constant value for x greater than or equal t o 0.3. The exponential decay is interpreted as incoherent scattering b y random scatterers (Al atoms), and the small constant value presumabl y originates from the fluctuations induced by acoustic and localized m odes. On the other hand, when the phonon lifetime and the clustering e ffect are considered, the transmission coefficient is enhanced, and th e I dependence of the coefficient is significantly modified. In partic ular, the saturation of the transmission coefficient for x less than o r similar to 0.3 reported in a recent experiment is shown to be explai nable in terms of the clustering of like atoms in the alloy barrier.