82 lines
5.9 KiB
XML
82 lines
5.9 KiB
XML
= Introduction
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4H-SiC 性能很好、器件应用广泛，因此需要开发原位的、非破坏性的表征技术。
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4H-SiC 是一种具有优良性质的半导体材料，包括宽禁带、高临界电场强度、高热导率和沿 c 轴的高电子迁移率，因此受到了广泛的研究。
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受益于外延技术的发展和新能源产业的需求增长，4H-SiC 在功率电子器件中得到了广泛应用。
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然而，4H-SiC 器件的性能仍然受到缺陷的限制，如何在生长和工作条件下避免缺陷的产生仍然是一个挑战。
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此外，用于表征 SiC 掺杂的方案（如二次离子质谱（SIMS）和霍尔效应测量）通常是破坏性的且耗时，因此迫切需要开发原位和非破坏性的表征技术。
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// 随着尺寸缩小，4H-SiC 中的缺陷对器件性能的影响更加显著。（纳米材料？
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The 4H-silicon carbide (SiC) has long attracted a lot of research
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thanks to its wider bandgap, higher critical electric field strength,
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higher thermal conductivity, and higher electron mobility along the c-axis
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than silicon (Si) and gallium arsenide (GaAs) as well as other SiC polytypes
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@casady_status_1996 @okumura_present_2006.
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It has been widely used in power electronic devices
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thanks to the development of epitaxy technology and the increasing application in the new energy industry
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@tsuchida_recent_2018 @harada_suppression_2022 @sun_selection_2022.
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However, the performance of 4H-SiC devices remains constrained by the presence of defects,
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which may be introduced during the growth process @nishio_triangular_2020 @demenet_tem_2005
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or arise under device operating conditions
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@mahadik_ultraviolet_2012 @okada_dependences_2018 @iwahashi_extension_2017 @caldwell_driving_2010
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@miyanagi_annealing_2006 @iijima_correlation_2017.
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Furthermore,
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conventional methods for characterizing the doping properties of SiC
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(such as secondary ion mass spectrometry (SIMS) @kudriavtsev_quantitative_2003 @kim_characteristics_2024
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and Hall effect measurements @noguchi_comparative_2021 @asada_hall_2016),
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are destructive and time-consuming.
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Therefore, there is a pressing need to develop an in-situ and non-destructive characterization techniques.
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拉曼主要体现声子的信息，并且早已经有应用，主要用来区分 SiC 的多型。
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声子（量子化的原子振动）在理解晶体的原子结构以及热电性质方面起着重要作用。
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声子可以通过多种实验技术来探测，包括 EELS、IR 吸收谱等。
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拉曼光谱是最常用的方法，它提供了一种无损、非接触、快速和局部的声子测量方法。
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早有关于拉曼的研究，且拉曼已被广泛用于区分 SiC 的多型。
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Phonons (quantized atomic vibrations) play a fundamental role
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in understanding the atomic structure as well as the thermal and electrical properties of semiconductors.
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They could be probed by various experimental techniques,
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such as electron energy loss spectroscopy @yan_single-defect_2021 @egoavil_atomic_2014
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and infrared absorption spectroscopy @pluchery_infrared_2012 @tong_temperature-dependent_2018.
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Among these techniques,
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Raman spectroscopy is the most commonly used method,
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// TODO: 增加一些引用，可以先不用收集文献给这里，最后把其它部分的全拿过来就行了。
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as it provides non-destructive, non-contact, rapid and spatially localized measurement of phonons
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that near the #sym.Gamma point in reciprocal space.
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Studies in Raman scattering of 4H-SiC have been conducted since as early as 1968 @feldman_phonon_1968
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and nowadays have been widely employed to identification of different SiC polytypes
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@guo_characterization_2012 @yan_study_2016 @hundhausen_characterization_2008 @nakashima_raman_2013.
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拉曼谱中有更多信息。有一些新的研究，但他们还有不足。
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近年来，更多信息被从拉曼光谱中挖掘出来。
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LO 声子峰或 LOPC 峰已经被证明与自由载流子的类型和浓度有关，它们已经被用于估计离子注入层的厚度和 n 型 SiC 的掺杂浓度。
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3C-SiC 的一类层错的拉曼和 EELS 光谱已经被研究，但更多类型的层错及其在 4H-SiC 中的拉曼光谱还没有被研究。
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有人提出了可能的 N 掺杂原子的拉曼峰，但并没有在实验上对比验证，同时 Al 或其它点缺陷的拉曼峰也缺少系统的研究。
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此外，拉曼光谱上仍有一些不知来源的峰；同时，也缺少一些理论上预测应该存在的峰。
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// TODO: 总结更多文献
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In recent years, increasingly rich information has been extracted from Raman spectra of 4H-SiC.
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Longitudinal optical phonon–plasmon coupling (LOPC) peek
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has been utilized to rapidly estimate the doping concentration in n-type SiC @harima_raman_1995
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and to identify doping type in different layers @song_depth_2020,
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while the influence of free carriers on the LO phonon peek in p-type SiC
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has not been systematically investigated yet.
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Peeks associated with one type of stacking faults in 3C-SiC have been investigated @yan_single-defect_2021,
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while other types of stacking faults and their Raman spectra in 4H-SiC remain unexplored.
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Peeks associated with nitrogen dopants have been proposed @_n-sic_2010
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but have not been experimentally verified,
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while systematic studies on the Raman spectra of aluminum or other point defects are still lacking.
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Moreover, certain phonon modes predicted by theory remain unobserved,
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while there are still some unidentified peaks in the Raman spectra.
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本文通过三种方式，研究 4H-SiC 中带缺陷和不带缺陷的声子。我们第一次做到了什么什么。
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In this paper, we explored the phonon in 4H-SiC by three ways:
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symmetry analysis, first-principles calculations, and Raman experiment.
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We first investigated the phonon modes in perfect 4H-SiC,
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and then explored the phonon modes associated with defects and doping.
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// TODO: 描述自己做了什么，强调自己是第一次做到了什么。
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