二维MoS2的掺杂及其同质pn结型光电探测器件研究

Molybdenum disulfide (MoS2) has great application potential in novel two-dimension (2D) photodetectors due to its unique layered structure and distinct physical properties such as tunable energy band, high absorption coefficient, etc. However controllable fabrication of 2D MoS2 pn homojunction that beneficial for photoresponse enhancement of detectors is quite a challenging subject at present. A favorable doping method needs to be explored urgently for exerting the advantages of 2D MoS2 pn homojunction interface as well as preparation of stable 2D p-type MoS2. Base on these issues, our project aim to grow 2D p-type MoS2 via one-step substitutional doping method by employing chemical vapor deposition technique which is conducive to the stability of doped 2D MoS2 and the performance optimization of devices. Niobium halide is selected as controllable doping precursor and substrates that able to suppress nucleation events, possess small lattice mismatch and be free of dangling bonds, are utilized such as molten glass, hexagonal boron nitride and so forth. 2D MoS2 pn homojunctions with controllable interfaces and good optoelectronic characteristics will be built, and achieve their application in high-performance photodetectors. Simultaneously, the doping mechanisms including the relations between the growth condition and properties of materials and devices will be investigated systematically. The successful implementation of this project has great practical values for the development of 2D photodetectors, and will provide reliable scientific basis and experimental approach for effective 2D MoS2 p-type doping and pn homojunction preparation under control.

二硫化钼（MoS2）凭借其独特的层状结构和能带可调、吸收系数高等物理性质，在新型二维光电探测器件方面展现出了巨大的应用潜力。但目前可控制备益于探测器光响应提高的二维MoS2同质pn结是一个极具挑战性的课题，利于二维MoS2同质pn结界面优势发挥及稳定二维p型 MoS2获得的掺杂方法还亟待探索。针对上述难题，本课题拟采用利于掺杂二维MoS2稳定性及其器件性能优化的化学气相沉积技术, 以可抑制成核和低失配、不含表面悬挂键的熔融玻璃、六方氮化硼等为衬底，选择铌的卤化物作为可控掺杂前驱体，一步法替位掺杂生长二维p型MoS2，构建具有可控界面和良好光电性质的二维MoS2同质pn结,实现其高性能光电探测器件应用；同时，系统研究掺杂机制以及生长条件与材料和器件性能的关系。本课题的实施将为二维MoS2 有效p型掺杂及可控同质pn结制备提供可靠的科学依据及实验途径，对二维光电探测器件的发展有重要的实践价值。

二维材料因其独特的物理结构和优异的光电特性在新型光电器件领域显示出了巨大的应用前景。MoS2作为二维材料家族中的重要成员，具有可调的能带结构和较高的光子利用率，使其非常适合作为光电探测器件的工作介质。尽管已经有很多关于MoS2基异质结光电器件的报道，但具有其自身独特优势的二维MoS2同质结还是必不可少的。对比其他掺杂方式，在化学气相沉积（CVD）过程中替位掺杂更稳定并且更利于二维MoS2同质结的制备。然而，目前利用CVD可控直接生长的二维p型MoS2和获得其基础上的二维同质结仍然是两个极具挑战性的难题。本项目中，我们选择挥发性更强、更好控制其分压的Nb的卤化物作为掺杂前驱体，通过CVD过程中一步替位掺杂生长二维p型MoS2并将其直接生长于二维n型MoS2上构建其同质pn结型器件。二维p型MoS2的载流子迁移率可以达到2.5cm2V-1s-1。同时我们还研究了Nb掺杂对二维p型MoS2结晶及光、电等性质的影响。将获得的二维MoS2同质pn结作为工作介质实现了自供能型光电探测器件，在无外加偏压下器件响应度达178mAW−1，且稳定性良好。该项目的科学意义在于其将对丰富二维MoS2乃至二维材料特性及发挥其在高性能光电探测器件应用方面的潜力具有重要的实践价值。在本项目资助下，项目组人员共发表论文15篇，其中，SCI论文10篇，EI论文2篇，申请专利2项，已授权1项，培养硕士研究生4名。