ABSTRACT
This chapter introduces the physical origins of ZT enhancement by engineering thermal and electronic transport in low-dimensional materials with focus on the examples of superlattices and nanowires for high power factor and low thermal conductivity, respectively. Heavily-doped semiconductors are perhaps the most promising class of thermoelectric materials. Insulators do not have enough conduction electrons, and metals suffer from very small Seebeck coefficient values. The chapter summarizes different proposals to minimize ionized impurity scattering in thermoelectric materials and devices. Many groups have used the nanoparticle-doping approach to enhance the thermoelectric properties of thermoelectric materials. Another approach to limit ionized impurity scattering is to use modulation doping. The idea of modulation doping was first proposed in two-dimensional structures. Thermoelectric materials used in commercial applications are bulk semiconductors, and must be cost effective to be commercially viable. Semiconductors are filling the gap between insulators and metals.
