周期铁电调制单层TMD激子弛豫特性及光电探测器研究

近年来，调控激子弛豫过程的光电器件吸引了广泛关注。单层过渡金属硫族化物（TMDs）具有直接带隙及大激子结合能，在室温下单层TMDs中光生载流子展现出明显的多粒子库伦相互作用，具有多重弛豫过程，为激子弛豫调控提供了便利。尽管TMDs中激子弛豫特性可以通过栅极、静电掺杂和应变等手段进行调控，但如何进一步提高激子调控能力，并且应用到实际光电器件中还面临很多挑战。本项目拟采用周期性极化铁电基底，通过静电掺杂，调控单层TMDs激子弛豫特性。使用域工程化的铌酸锂产生的周期性表面电荷分布，改变TMDs中自由载流子密度空间分布，进而调控其空间PL特性。同时，通过栅极进一步调控其能带结构，构建同晶pn异质结，实现载流子的电限制和操纵，并操控畴壁光电子的迁移，以构建高性能光电探测器。该项目可以通过简便手段调控单层TMDs自由载流子密度分布和激子弛豫特性，为高性能光电探测器的研发提供了物理基础和设计思路。

Recently, the emerging optoelectronic devices have attracted enormous attentions due to the manipulation of the excitons. Single-layer transition metal chalcogenides (TMDs) show a direct band gap and large exciton binding energy. The excitons in TMDs exhibit obvious multi-particle Coulomb interactions at room temperature, and have multiple relaxations paths, which provides convenience for exciton modulation. Although the exciton relaxation characteristics of TMDs can be adjusted by gate voltage, electrostatic doping and strain-stress effect, there are still many challenges in how to control the exciton emission and apply it into actual optoelectronic devices. This project intends to use periodically polarized Lithium Niobate as the substrate, and adjust the spacial exciton relaxation characteristics of single-layer TMDs through electrostatic doping. The periodical surface charge distribution generated by the domain-engineered in Lithium Niobate is used to change the spatial distribution of free carrier density in the monolayer TMDs, thereby modulating its spatial PL emission. Meanwhile, the band gap is further manipulated through the electrodes to realize the electrical confinement and manipulation of the carriers, forming the pn homojunction and regulating the migration of photoelectrons around the domain walls, to construct a high-performance photodetector. The electrical generation and control of excitons provide a route for for the application of high-performance optoelectronic devices with complete electrical tunability.