Ohta Hiromichi, Kim Sung Wng, Kaneki Shota, Yamamoto Atsushi, Hashizume Tamotsu
Research Institute for Electronic Science Hokkaido University N20W10, Kita Sapporo 001-0020 Japan.
Graduate School of Information Science and Technology Hokkaido University N14W9, Kita Sapporo 060-0814 Japan.
Adv Sci (Weinh). 2017 Nov 24;5(1):1700696. doi: 10.1002/advs.201700696. eCollection 2018 Jan.
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 (), high electrical conductivity (σ), and low thermal conductivity (κ). State-of-the-art nanostructuring techniques that significantly reduce κ have realized high-performance thermoelectric materials with a figure of merit ( = ∙σ∙∙κ) between 1.5 and 2. Although the power factor (PF = ∙σ) must also be enhanced to further improve , the maximum PF remains near 1.5-4 mW m K due to the well-known trade-off relationship between and σ. At a maximized PF, σ 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 and σ of the high-mobility electron gas from -490 µV K and ≈10 S cm to -90 µV K and ≈10 S cm, while maintaining a high carrier mobility (≈1500 cm V s). The maximized PF of the high-mobility electron gas is ≈9 mW m K, which is a two- to sixfold increase compared to state-of-the-art practical thermoelectric materials.
热电转换是一种能量收集技术，它通过具有大热电势（）、高电导率（σ）和低导热率（κ）的热电材料的塞贝克效应，将来自各种来源的废热直接转化为电能。显著降低κ的先进纳米结构技术已经实现了优值（ = ∙σ∙∙κ）在1.5至2之间的高性能热电材料。尽管为了进一步提高还必须提高功率因数（PF = ∙σ），但由于和σ之间众所周知的权衡关系，最大PF仍保持在1.5 - 4 mW m K附近。在最大化的PF下，σ远低于理想值，因为杂质掺杂会抑制载流子迁移率。在AlGaN/GaN异质结构上制备了金属氧化物半导体高电子迁移率晶体管（MOS-HEMT）结构。向MOS-HEMT施加栅极电场会同时调制高迁移率电子气的和σ，从 - 490 µV K和≈10 S cm变为 - 90 µV K和≈10 S cm，同时保持高载流子迁移率（≈1500 cm V s）。高迁移率电子气的最大化PF约为9 mW m K，与最先进的实用热电材料相比提高了两到六倍。
