Photoacoustic spectra and thermoelectric properties of amorphous Si/Au/Ge/Au superlattice

Abstract

The amorphous Si-Ge-Au superlattice shows highly superior thermoelectric properties. In this paper, we describe the photoacoustic spectra and thermoelectric properties of these materials with various Au concentrations and discuss the mechanism responsible for high thermoelectric properties. Amorphous Si/Au/Ge/Au superlattice was prepared by alternate deposition of Si, Ge and Au. The Au concentration dependence of electric and optical properties was measured. We investigated the band structure of amorphous Si-Ge-Au over a wide energy range by combining the electrical and optical measurements. The energy range was from 0.01 (the impurity level of the Au dopant) to 2 eV (band edge). We found that the Au atoms in amorphous Si-Ge not only produce strong potential fluctuations but also act as acceptor impurities. © 2008 The Japan Society of Applied Physics.