深能级对窄带隙Bi2Te3基合金的少子调控及其热电性能优化

少数载流子激发引起的双极扩散效应是限制窄带隙热电材料性能提升的主要因素。深能级普遍存在于半导体材料中，且对少数载流子和热电传输参数有着重要影响。因而，本项目提出深能级工程以调控少数载流子，并选择具有典型晶体结构和重要应用背景的Bi2Te3基合金为研究对象来表明这种新策略的有效性。本项目拟结合第一性原理计算和深能级瞬态谱测试，研究第三主族元素掺杂对深能级的类型、能量位置、空穴和电子的俘获截面、浓度及其分布等物理性质的影响，揭示窄带隙热电材料中深能级的形成原因及调控机制；研究深能级对少子浓度、迁移率、有效质量、寿命等参数的影响，阐明深能级工程对双极扩散效应的抑制机理；研究深能级对载流子和声子输运的作用机制，探索通过深浅能级的交互作用实现Bi2Te3基合金热电优值的显著提高。本项目的研究不仅加深了对深能级物理学的认识和理解，而且为深能级工程在其他窄带隙热电和功能材料中的应用提供了方向和指导。

The major obstacle limiting the thermoelectric performance of narrow bandgap semiconductors is the bipolar effects induced by minority carrier excitation. Deep levels are ubiquitous in semiconductors, which play significant roles on the minority carriers and thermoelectric transport parameters. Herein, deep level engineering is introduced to regulate minority carriers. And the effectiveness of this strategy is demonstrated on the Bi2Te3 based alloys, which have the typical crystal structure and great application prospect. The effects of group Ⅲ elements doping on the physical properties of deep level, including defect type, energy position, hole- and electron-capture cross section, concentration and concentration profiles, are thoroughly studied by the first principle calculation and deep level transient spectroscopy. And then the reason of deep level formation and its regulation mechanism in narrow bandgap thermoelectric materials would be clarified. The impacts of deep level on the concentration, mobility, effective mass and lifetime of minority carrier are investigated and then its inhibition mechanism on bipolar effect should be clear. By revealing the impacts of deep level on the carrier and phonon transport, we explore the possibility of thermoelectric performance breakthrough for Bi2Te3 based alloys by the interplay between the shallow and deep level in-gap states. This work not only deepens the understanding of deep level physics, but also provides direction and guidance for the application of deep level engineering in other narrow bandgap thermoelectric and functional materials.