Defect Characterization and Control in Metastable GeSn Optoelectronic Alloy Nanostructures

亚稳态 GeSn 光电合金纳米结构的缺陷表征与控制

• 批准号: 2003266
• 负责人: Paul McIntyre
• 金额: $ 48.12万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2003266&HistoricalAwards=false
• 关键词: Defect; Characterization; Control; Metastable; GeSn

Nontechnical DescriptionAn important area of application for semiconductor materials is in optoelectronic devices; for example, in devices such as lasers or light-emitting-diodes (LED’s) that use electrons to stimulate the emission of light. There is great interest, both scientifically and technologically, in semiconductors that can emit light with wavelengths somewhat longer than visible light, i.e. in the mid-infrared part of the spectrum. Such light sources, when fabricated on silicon chips, could become key components in future ubiquitous chemical sensor networks, in speeding up data transfer between and on silicon chips, and in motion sensors required by autonomous vehicles. This research project focuses on a semiconductor material system, germanium-tin, that holds great promise for mid-infrared light emission on silicon chips. The efficiency of light emission by germanium-tin is limited by the presence of atomic scale defects that grow into the material when it is synthesized. This project characterizes the nature and number of such defects, and investigates methods for annihilating or altering them to minimize their effects on germanium-tin. Undergraduates are involved in these research activities, with special efforts made to recruit highly competitive undergraduate researchers from groups that are under-represented in the US science and engineering workforce. The project includes a partnership with Stanford’s RISE outreach program, to inspire high school students to consider further education and careers in STEM fields.Technical DescriptionExhibiting a direct bandgap at sufficiently large (x ~ 10 atomic %) tin composition, Ge(1-x)Sn(x) alloys hold great promise for mid-infrared (IR) light emitters and absorbers, while also being monolithically compatible with silicon electronic and photonic technologies. Previous research on germanium-tin epitaxial films grown on silicon has demonstrated mid-IR optically-pumped lasing, and there has been a gradual trend of increasing Sn content to access longer wavelength operation. The light emission characteristics of Ge(1-x)Sn(x) are still far from optimal. Low growth temperatures ( 300°C) used to promote high Sn content alloys cause large concentrations of acceptor-type vacancy defects to form. Strong pairing of Sn atoms with these vacancies is predicted theoretically and will result in enhanced non-radiative carrier recombination, reducing the efficiency of light emission and absorption. This project uses strain-engineered core-shell nanowire structures as a platform to study post-growth annealing to dissociate Sn-vacancy pairs and to annihilate vacancies incorporated in the Ge(1-x)Sn(x) shells during their growth. Shells of thickness up to 500 nm are of particular interest, to achieve wire structures capable of efficiently guiding mid-IR light. Synchrotron diffuse x-ray scattering is used to characterize trends in the relative concentration of vacancies bound to Sn atoms, divacancies, clusters and monovacancies in the alloys versus annealing time and temperature. A key goal is to understand the rates and mechanisms governing the approach to vacancy equilibrium in these alloys. Extended x-ray absorption fine structure analysis provides an additional probe of local bonding around Sn atoms and the stability of Sn-vacancy pairs. The project also examines atomic fluorine as a chemical vacancy passivant, building on prior experience with F passivation of Si surface states and vacancies in Ge. Coupling between x-ray and optoelectronic characterization of the core-shell wires can reveal fundamental insights into the connection between point defects and device-relevant properties. Temperature-dependent photoluminescence, photoconductivity and ultra-fast pump-probe measurements are used to probe Ge(1-x)Sn(x) band structure and the effects of different vacancy defect populations on carrier recombination dynamics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术描述的半导体材料应用的重要领域是光电设备中的；例如，在使用电子刺激光发射的激光器或发光二极管（LED）等设备中。从科学和技术上，在半导体上都有极大的兴趣，这些半导体可以发出比可见光更长的波长发光的光线，即在频谱的中红外部分。当在硅芯片上制造时，这种光源可能会成为未来无处不在的化学传感器网络中的关键组件，从而加快了硅芯片和硅芯片之间的数据传输以及自动驾驶汽车所需的运动传感器。该研究项目的重点是半导体材料系统，即锗锡，该系统对硅芯片上的中红外光发射具有巨大的希望。锗键发射发射的效率受原子量表缺陷的存在限制，这些缺陷在合成后生长成该材料。该项目表征了此类缺陷的性质和数量，并研究了歼灭或改变它们以最大程度地减少其对锗锡的影响的方法。本科生参与了这些研究活动，并在美国科学和工程劳动力中招募竞争激烈的本科研究人员做出了特别努力。该项目包括与斯坦福大学的崛起外展计划的合作伙伴关系，以激发高中生考虑在STEM领域的进一步教育和职业。技术描述可以在足够大的（x〜10个原子）锡组成（X〜10）锡（1-X）SN（1-X）SN（x）SN（x）SN（x）SN（X）合金中，同时构成中型（IR）光线充电器，并具有孤立的光电孔，并具有很大的希望。技术。先前关于在硅上生长的锗键外延膜的研究证明了中IR光学泵送的激光，并且已经存在增加SN含量以访问更长波长操作的级趋势。 GE（1-X）SN（X）的光发射特性仍然远非最佳。用于促进高SN含量合金的低生长温度（300°C）会导致大量的受体型空位缺陷形成。 SN原子与这些空缺的强大配对将被预测，并将导致增强的非辐射载体重组，从而降低发光和滥用的效率。该项目使用应变设计的核心壳纳米线结构作为一个平台，用于研究生长后的生长后，以分离GE（1-X）SN（x）壳中掺入的SN-VACACACES。高达500 nm的厚度的壳特别感兴趣，以实现能够有效引导MID-IR光的电线结构。同步加速器弥漫性X射线散射用于表征与SN原子，Divacances，DivaCances，Clusters和Monovacances在合金相对于退火时间和温度的相对浓度的趋势。一个关键目标是了解这些合金中处理疫苗的方法的速率和机制。扩展的X射线抽象精细结构分析提供了SN原子周围局部键合的附加探针以及SN-VACANCANCANCY对的稳定性。该项目还研究原子氟作为一种化学空缺钝化物，它基于先前的经验，以f钝化Si表面状态和GE中的空位。 X射线和光电子表征之间的耦合可以揭示有关点缺陷与设备相关属性之间连接的基本见解。温度依赖性的光致发光，光电导率和超快速的泵浦探针测量用于探测GE（1-X）SN（X）频带结构以及不同空位缺陷种群对载载建议动态的影响。该奖项反映了NSF的法定任务，并通过使用基础的智力效果评估来评估NSF的法定任务，并以良好的评价来综述。

项目成果

Oxide Decomposition and Sn Surface Segregation on Core/Shell Ge/GeSn Nanowires

• DOI: 10.1021/acsaelm.2c01061
• 发表时间: 2022-11
• 期刊: ACS Applied Electronic Materials
• 影响因子: 4.7
• 作者: M. Braun;J. Lentz;Ishaa Bishnoi;A. Meng;L. Casalena;Huikai Cheng;P. McIntyre

Bending and precipitate formation mechanisms in epitaxial Ge-core/GeSn-shell nanowires

• DOI: 10.1039/d1nr04220c
• 发表时间: 2021-10-05
• 期刊: NANOSCALE
• 影响因子: 6.7
• 作者: Meng, Andrew C.;Wang, Yanming;McIntyre, Paul C.
• 通讯作者: McIntyre, Paul C.

Local ordering in Ge/Ge–Sn semiconductor alloy core/shell nanowires revealed by extended x-ray absorption fine structure (EXAFS)

• DOI: 10.1063/5.0136746
• 发表时间: 2023-02
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: J. Lentz;J. Woicik;Matthew Bergschneider;Ryan C. Davis;Aranyak Mehta;Kyeongjae Cho;P. McIntyre