Phonon engineering in nanostructures for solid-state energy conversion

Solid-state energy conversion technologies such as thermoelectric and therm ionic refrigeration and power generation require materials with low thermal conductivity but good electrical conductivity, which are difficult to real ize in bulk semiconductors. Nanostructures such as quantum wires and quantu m wells provide alternative approaches to improve the solid-state energy co nversion efficiency through size effects on the electron and phonon transpo rt. In this paper, we discuss the possibility of engineering the phonon tra nsport in nanostructures, with emphases on the thermal conductivity of supe rlattices. Following a general discussion on the directions for reducing th e lattice thermal conductivity in nanostructures, specific modeling results on the phonon transport in superlattices will be presented and compared wi th recent experimental studies to illustrate the potential approaches and r emaining questions. (C) 2000 Elsevier Science S.A. All rights reserved.