Thermopower of Amorphous Chalcogenides under Photoexcitation

摘要

Thermopower and conductivity in the dark and under photo excitation have been measured on a-As_2Te_3 and a-As_2Se_3. The analysis of photoequilibrium data suggests that both ambipolar and unipolar actions may be responsible for the conduction process for the materials. Photoconductivity measurement further confirms that for a-As_2Te_3, the contribution by electrons to the conduction is significant, and a small polaron model can be used to explain such phenomenon. Photothermopower on a-As_2Te_3 further enhances the concept of p-type conduction on chalcogenides. The complex photothermopower characteristic of a-As_2Te_3 indicates that phonon drag is mainly responsible for such behaviour.