Cross-plane thermal conductivity reduction of vertically uncorrelated Ge/Si quantum dot superlattices

A drastic reduction in temperature dependent cross-plane thermal conductivity K-perpendicular to occurs in Ge quantum dot superlattices (QDSLs), depending on the vertical correlation between dots. Measurements show at least a twofold decrease of kappa(perpendicular to) in uncorrelated dot structures as compared to structures with the same Si spacer of 20 nm but good vertical dot alignment. The observed impact of disorder on the conductivity provides an alternative route to reduce the thermal conductivity of QDSLs. The results of this work have implications for the development of highly efficient thermoelectric materials and on-chip nanocooling devices. (C) 2008 American Institute of Physics.