物理化学学报 >> 2020, Vol. 36 >> Issue (1): 1907004.doi: 10.3866/PKU.WHXB201907004

所属专题: 庆祝唐有祺院士百岁华诞特刊

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新型石墨烯基LED器件:从生长机理到器件特性

陈召龙1,2,高鹏2,3,*(),刘忠范1,2,*()   

  1. 1 北京大学化学与分子工程学院,北京分子科学国家研究中心,北京大学纳米化学研究中心,北京 100871
    2 北京石墨烯研究院,北京 100095
    3 北京大学电子显微镜实验室,北京大学量子材料研究中心,量子物质科学研究中心,北京 100871
  • 收稿日期:2019-07-01 录用日期:2019-08-27 发布日期:2019-09-03
  • 通讯作者: 高鹏,刘忠范 E-mail:p-gao@pku.edu.cn;zfliu@pku.edu.cn
  • 作者简介:高鹏,北京大学物理学院研究员,博士生导师。2005年获中国科学技术大学物理学学士,2010年获中国科学院物理研究所凝聚态物理学博士学位。主要研究方向为电子显微学、晶体与低维材料的界面结构|刘忠范,1962年出生。1990年获东京大学博士学位;现为北京大学教授,博士生导师,北京石墨烯研究员院长,中国科学院院士。主要研究方向为石墨烯的CVD生长方法与应用
  • 基金资助:
    国家重点基础研究发展规划项目(973)(2016YFA0200103);国家自然科学基金(51432002);国家自然科学基金(51290272);北京市科学技术委员会(Z181100004818002)

Graphene-Based LED: from Principle to Devices

Zhaolong Chen1,2,Peng Gao2,3,*(),Zhongfan Liu1,2,*()   

  1. 1 Center of NanoChemistry, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
    2 Beijing Graphene Institute (BGI), Beijing 100095, P. R. China
    3 Electron Microscopy Laboratory and International Center for Quantum Materials, Peking University, Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China
  • Received:2019-07-01 Accepted:2019-08-27 Published:2019-09-03
  • Contact: Peng Gao,Zhongfan Liu E-mail:p-gao@pku.edu.cn;zfliu@pku.edu.cn
  • Supported by:
    the National Key Basic Research Program of China (973)(2016YFA0200103);the National Natural Science Foundation of China(51432002);the National Natural Science Foundation of China(51290272);the Beijing Municipal Science and Technology Planning Project, China(Z181100004818002)

摘要:

Ⅲ族氮化物因具有禁带宽度大、击穿电压高、电子饱和漂移速度大、稳定性高等优异特性而广泛应用在发光二极管(LED)、激光器以及高频器件中。目前Ⅲ族氮化物薄膜通常是异质外延生长在蓝宝石衬底表面,但是由于蓝宝石与Ⅲ族氮化物之间存在较大的晶格失配与热失配,使得外延生长的Ⅲ族氮化物内部存在较大的应力与较高的位错密度,严重影响了器件性能;与此同时,蓝宝石衬底热导率差,限制了其在大功率器件方面的应用。近年来研究发现,石墨烯作为外延生长缓冲层,能够有效解决蓝宝石衬底与外延Ⅲ族氮化物薄膜之间由于晶格失配和热失配导致的高应力与高位错密度等问题,进而获得了高品质薄膜,并提升了器件的性能。本文综述了石墨烯/蓝宝石衬底上Ⅲ族氮化物生长与LED器件构筑的研究现状,着重介绍了本课题组提出的一种新型外延衬底—石墨烯/蓝宝石衬底的特点,阐明了Ⅲ族氮化物在该新型衬底上的生长机理,总结了其对Ⅲ族氮化物质量提升的作用,并对其发展前景进行了展望。

关键词: 石墨烯, 化学气相沉积, 蓝宝石, Ⅲ族氮化物, LED, 准范德华外延

Abstract:

Group-Ⅲ nitride (Ⅲ-N) films have numerous applications in LEDs, lasers, and high-power/high-frequency electronic devices because of their direct wide band gap, high breakdown voltage, high saturation velocity of electrons, and high stability. Commercial Ⅲ-N films are usually heteroepitaxially grown on c-sapphire substrate by metal-organic chemical vapor deposition (MOCVD). However, relatively large mismatches occur in the in-plane lattice and thermal expansion between the Ⅲ-N films and sapphire substrates, which lead to high stress and high dislocation density in epilayers that reduce the performance of the LED. Moreover, the poor thermal conductivity of sapphire substrate also hinders many applications. Recently, graphene was used as a buffer layer to overcome the mismatch between Ⅲ-N films and substrates by utilizing van der Waals epitaxy and improving heat dissipation. In this review article, we consider the recent progress in the development of a new type of epitaxial substrate, the so-called "graphene/sapphire substrate" for Ⅲ-N film growth and LED applications. The growth mechanisms are summarized and future prospects are proposed. The article is divided into three parts.

1. The synthesis of graphene/sapphire substrate. High-quality monolayer graphene is directly synthesized on sapphire substrates (flat substrate and nanopatterned substrate) by metal-catalyst-free CVD method. The method does not depend on the metal catalyst nor involve a complex and highly technical transfer process, and is compatible with the MOCVD and molecular beam epitaxy process.

2. Growth of high-quality Ⅲ-N films on graphene/sapphire substrates. The nucleation of Ⅲ-N on graphene can be tuned by the density of defects in the graphene film. N2 plasma treatment of the graphene/sapphire substrate can increase the nucleation sites for Ⅲ-N growth by introducing pyrrolic nitrogen doping. Epitaxial lateral overgrowth of the Ⅲ-N is promoted on the graphene/sapphire substrate owing to the relatively lower diffusion barrier of atoms on graphene. Consequently, the biaxial stress in group-Ⅲ nitride is significantly decreased while the dislocation density is reduced even without a low-temperature buffer layer. Moreover, vertically-oriented graphene nanowalls can effectively improve the heat dissipation in AlN films.

3. High-performance LEDs on graphene/sapphire substrate. High-quality Ⅲ-N films obtained on graphene/sapphire substrates enable LED fabrication. The as-fabricated LEDs on graphene/sapphire substrate deliver much higher light output power compared with that on bare sapphire substrate. The as-fabricated LEDs have low turn-on voltage, high output power, and good reliability. Graphene can also be utilized as transfer medium or transparent conductive electrode to boost LED performance.

Key words: Graphene, Chemical vapor deposition, Sapphire, Group-Ⅲ nitride films, LED, Van der Waals epitaxy

MSC2000: 

  • O649