【作者】 李晨；

【导师】 甘雪涛；

【作者基本信息】 西北工业大学 ， 光学工程， 2022， 硕士

【摘要】 大数据、云计算等信息业务的蓬勃发展为硅基光电子技术发展提供了巨大的机遇,然而硅基集成的有源光电子器件（光源、探测器等）受到硅的间接带隙影响,难以实现高性能。通过异质集成锗、III–V族半导体等材料,可以在硅基光电子集成回路上实现有源功能。但是这些传统半导体材料的集成和器件制备需要非常复杂的异质生长、键合、离子注入、选择性刻蚀等工艺,并且会引入晶格失配、缺陷等问题,降低器件性能。二维材料表面不存在悬挂键,可通过范德瓦尔斯力与任意衬底或结构集成,避免晶格失配等问题,是一种很有潜力的异质集成有源材料。此外,二维材料仅有原子层厚度,可以通过静电场有效地进行电子或空穴的掺杂,实现多种有源器件功能。然而,p-n结作为实现有源器件的关键结构,目前在硅基集成二维材料中仍未被实现。本文在硅基光子晶体微腔和波导上集成少数原子层厚度的碲化钼（MoTe₂）,提出分离型硅背栅结构原位掺杂MoTe₂构建可调MoTe₂p-n结和p-i-n结的思路,基于所实现的高质量p-n结和p-i-n结实现了高性能的片上光电探测。主要研究内容如下:（1）硅基光子晶体微腔及波导的设计制备和实验表征。分别基于有限元法和时域有限差分法建立光子晶体微腔和光子晶体波导的数值计算模型。编写Lab VIEW程序并利用正交偏振显微共聚焦系统表征光子晶体微腔的共振模式及空间模式分布;编写Lab VIEW程序并利用垂直光栅型波导耦合系统表征光子晶体波导的传输谱。（2）基于光子晶体微腔的MoTe₂ p-n同质结光电探测器。利用金属分离栅极通过静电掺杂构建了MoTe₂ p-n同质结,证实了MoTe₂的双极性及其作为p-n同质结的特性。设计具有狭缝且电学隔离的光子晶体微腔,并集成MoTe₂,利用被狭缝缺陷分为两部分的微腔直接作为两个独立的背栅电极,不仅消除了金属电极的光吸收,同样缩减了制备流程,形成高质量的MoTe₂p-n同质结,理想因子接近于1.0且暗电流低至0.14 n A。由于微腔增强了光与物质的相互作用,在MoTe₂的吸收带边1353.7 nm处实现高达156m A/W的光响应,响应带宽高达1.1 GHz。（3）基于光子晶体波导的MoTe₂ p-i-n同质结光电探测器。将光子晶体波导设计为具有电学隔离的三部分,其中中间部分为导光的波导区域,两侧可独立提供硅背栅,将少层MoTe₂集成于其上,直接通过光子晶体波导两侧背栅对MoTe₂静电掺杂,构建了可重构的p-i-n同质结,理想因子接近于1.0且暗电流低于90 p A。p-i-n结工作模式下在1302 nm处实现400 m A/W的高响应率,归一化光暗电流比达到极高的10⁶ m W^-1。所构建的超低暗电流、高响应率和快速响应的高性能片上光电探测器为弱光探测提供新的思路,推动了片上集成光电子芯片的发展。更多还原

【Abstract】 The vigorous development of information services such as big data and cloud computing has provided huge opportunities for the progress of silicon photonics.However,silicon-based integrated active optoelectronic devices（light sources,photodetectors,etc.）are affected by the indirect band gap of silicon,which is difficult to achieve high performance.Active functions can be realized on silicon-based optoelectronic integrated circuits through hetero-integration of germanium,III–V semiconductors,etc.Nonetheless,the integration and device preparation of these traditional semiconductor materials require very complex processes such as hetero-growth,bonding,ion implantation and selective etching,and could introduce lattice mismatch,defects and other problems,reducing device performance.Two dimensional（2D）materials are promising materials for heterointegrated optoelectronic devices.The weak interlayer van der Waals forces allow 2D materials to be free of surface dangling bonds,promising their depositions on various substrates or structures without lattice mismatch and other problems.In addition,2D materials only have a thickness of a few atomic layers,facilitating their effective electron-or hole-doping by electrostatic field to realize various active device functions.However,p-n junction has not yet been realized in silicon-based integrated 2D materials,which is the key structure for active devices.In this paper,molybdenum telluride（MoTe₂）with a thickness of a few atomic layers is integrated on silicon photonic crystal（PC）cavity and waveguide,respectively.The idea of in-situ doping of MoTe₂ by the split silicon back gate structures to construct tunable MoTe₂p-n junction and p-i-n junction is proposed.The realized high-quality p-n junction and p-i-n junction enable high performance on-chip photodetection.The main research contents are as follows:（1）Design,fabrication and characterization of silicon PC cavity and waveguide.Numerical models of silicon PC cavity and PC waveguide were established based on the finite element method and finite-difference time-domain method,respectively.The resonant modes and spatial mode distributions of PC cavity were measured by cross polarization confocal microscope and self-designed Lab VIEW programs.The transmission spectrum of PC waveguide was measured by photonic chip coupling system and self-designed Lab VIEW programs.（2）MoTe₂ p-n homojunction constructed on a PC cavity for photodetector.MoTe₂ p-n homojunction was constructed by electrostatic doping using the metal split gates,which confirmed the ambipolarity of MoTe₂ and its properties as a p-n homojunction.MoTe₂integrated with the PC cavity,which designed with air-slot and electrical isolation.The PC cavity divided into two parts by the air-slot was directly function as individual back-gate electrodes.The structure not only eliminates the optical absorption by metal electrodes,but reduces the fabrication processes.The realized high-quality p-n homojunction shows the ideality factors could approach 1.0 with a dark current less than 0.14 n A.With the PC cavity enhanced the light-MoTe₂ interaction,the high photoresponsivity of 156 m A/W was obtained at the wavelength of 1353.7 nm,which it’s the MoTe₂’s absorption bandedge.And the response bandwidth exceeded 1.1 GHz.（3）MoTe₂ p-i-n homojunction constructed on a PC waveguide for photodetector.The PC waveguide was designed as three parts with electrical isolation,which the middle part was the waveguide region for light guiding and both sides were directly act as individual back-gate electrodes.After integrating a few-layer MoTe₂ on PC waveguide,electrostatic doping builds a reconfigurable p-i-n homojunction with ideality factor close to 1.0 and dark current less than90 p A.In p-i-n homojunction configuration,a high photoresponsivity of 400 m A/W was achieved at 1302 nm,and the normalized photocurrent-to-dark-current ratio reached an extremely value of 10⁶m W^-1.The constructed high-performance on-chip photodetector with ultralow dark current,high responsivity and fast response speed provides a new idea for weak-light detection and promotes the development of integrated optoelectronic chips.更多还原