THERMOELECTRIC EFFECT OF SILICON FILMS WITH SHALLOW- AND DEEP-LEVEL ACCEPTORS

Abstract

Crystalline Si films with both shallow- and deep-level acceptors, Al and Cu , have been prepared on glass and quartz substrates by the methods of magnetron sputtering and Al -induced crystallization. Al and Cu are co-added in the Si films intermittently by regular pulse sputtering of Al and Cu targets during deposition of the Si films. By regulating the sputtering times of Al and Cu targets, the amounts of Al and Cu in the Si films can be controlled, and thus the Seebeck coefficient and electrical resistivity of the silicon films can be adjusted. It is found that the Al and Cu co-doped Si film has a larger Seebeck coefficient and a lower electrical resistivity at higher temperatures, as compared with that of only Al -doped Si film. As a result, the thermoelectric power factor of the Al and Cu co-doped Si film is greatly enhanced. The present experimental results will not only help us to understand the basic thermoelectric properties of semiconductors doubly doped with shallow- and deep-level impurities, but also open the possibility of enhancement of thermoelectric power factor by using this concept.