Enhanced Seebeck Coefficient of Amorphous Oxide Semiconductor Superlattices

We propose herein that amorphous oxide semiconductor (AOS) superlattices, which can be deposited on various substrate including glasses or plastics without any substrate heating, are appropriate for the realization of superlattice thermoelectric devices. As an example, thermoelectric properties of AOS superlattices composed of a-In-Zn-O (well) and a-In-Ga-Zn-O (barrier) layers, fabricated on SiO2 glass substrate by pulsed laser deposition at room temperature, were measured to clarify whether enhancement of Seebeck coefficient |S| occurs or not. The |S|2D value increases drastically with decreasing a-In-Zn-O thickness (dIZO) when the dIZO is < ∼5 nm, and reached 73 μV·K-1 (dIZO = 0.3 nm), which is ∼4 times larger than that of bulk |S|3D (19 μV·K-1), while it kept high electrical conductivity, clearly demonstrating that the quantum size effect can be utilized in AOS superlattices.