High Thermoelectric Power Factor of High-Mobility 2D Electron Gas

Thermoelectric conversion is an energy harvesting technology that directly converts waste heat from various sources into electricity by the Seebeck effect of thermoelectric materials with a large thermopower (S), high electrical conductivity (sigma), and low thermal conductivity (). State-of-the-art nanostructuring techniques that significantly reduce have realized high-performance thermoelectric materials with a figure of merit (ZT = S-2.sigma.T.(-1)) between 1.5 and 2. Although the power factor (PF = S-2.sigma) must also be enhanced to further improve ZT, the maximum PF remains near 1.5-4 mW m(-1) K-2 due to the well-known trade-off relationship between S and sigma. At a maximized PF, sigma is much lower than the ideal value since impurity doping suppresses the carrier mobility. A metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) structure on an AlGaN/GaN heterostructure is prepared. Applying a gate electric field to the MOS-HEMT simultaneously modulates S and sigma of the high-mobility electron gas from -490 mu V K-1 and approximate to 10(-1) S cm(-1) to -90 mu V K-1 and approximate to 10(4) S cm(-1), while maintaining a high carrier mobility (approximate to 1500 cm(2) V-1 s(-1)). The maximized PF of the high-mobility electron gas is approximate to 9 mW m(-1) K-2, which is a two- to sixfold increase compared to state-of-the-art practical thermoelectric materials.