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Selective area regrowth and doping for vertical gallium nitride power devices: Materials challenges and recent progress
Materials Today ( IF 24.2 ) Pub Date : 2021-05-26 , DOI: 10.1016/j.mattod.2021.04.011
Houqiang Fu , Kai Fu , Chen Yang , Hanxiao Liu , Kevin A. Hatch , Prudhvi Peri , Dinusha Herath Mudiyanselage , Bingjun Li , Tae-Hyeon Kim , Shanthan R. Alugubelli , Po-Yi Su , Daniel C. Messina , Xuguang Deng , Chi-Yin Cheng , Reza Vatan Meidanshahi , Xuanqi Huang , Hong Chen , Tsung-Han Yang , Jingan Zhou , Andrew M. Armstrong , Andrew A. Allerman , Edward T. Yu , Jung Han , Stephen M. Goodnick , David J. Smith , Robert J. Nemanich , Fernando A. Ponce , Yuji Zhao

This paper reviews materials challenges and recent progress for selective area regrowth and doping for vertical gallium nitride (GaN) power devices. The purpose is to realize randomly placed, reliable, contactable, and generally useable laterally patterned p-n junctions, which are the building blocks for various advanced power rectifiers and transistors. The general regrowth process and regrowth dynamics in trenches were discussed, where the effects of trench geometries, growth methods, and bulk substrates were elucidated. Comprehensive materials characterization techniques were utilized to analyze the regrown structures, including scanning electron microscopy, transmission electron microscopy, atom probe tomography, scanning probe microscopy, and secondary-ion mass spectrometry. Cathodoluminescence and secondary electrons in scanning electron microscopy and atom probe tomography were used to achieve lateral and vertical dopant profiling at a sub-micron scale. The regrowth interface after dry etching accumulated a high density of impurities and charges, contributing to the formation of a p+-n+ tunneling junction. This hypothesis was further confirmed by the electrostatic potential profile at the regrowth interface using electron holography. Novel etching technologies were investigated to improve the regrowth interface. It was found that low-power dry etching significantly reduced the interfacial charges and the reverse leakage currents of regrown p-n junctions. Photoelectrochemical wet etching was found to be effective in reducing deep-level defects near the regrowth interface. Atomic layer etching uses self-limiting chemical processes, thus removing the damaged layers without inducing further etching damage. Tertiarybutylchloride-based in situ etching may serve as an alternative etching method to dry etching with reduced etching damage. In terms of devices, regrown p-n junctions with low leakage currents and vertical junction field-effect transistors were demonstrated. Further improvements in selective area regrowth and associated devices can be expected using regrowth optimization and regrowth interface engineering via surface treatments and low-damage etching. These results represent an important step towards realizing selective area regrowth and doping for high performance GaN power electronics devices and systems.



中文翻译:

垂直氮化镓功率器件的选择性区域再生长和掺杂:材料挑战和最新进展

本文回顾了垂直氮化镓 (GaN) 功率器件的选择性区域再生长和掺杂的材料挑战和最新进展。目的是实现随机放置、可靠、可接触且普遍可用的横向图案化 pn 结,它们是各种先进功率整流器和晶体管的构建块。讨论了沟槽中的一般再生长过程和再生长动力学,其中阐明了沟槽几何形状、生长方法和块状衬底的影响。综合材料表征技术被用来分析再生结构,包括扫描电子显微镜、透射电子显微镜、原子探针断层扫描、扫描探针显微镜和二次离子质谱。扫描电子显微镜和原子探针断层扫描中的阴极发光和二次电子被用于实现亚微米级的横向和垂直掺杂分布。干蚀刻后的再生长界面积累了高密度的杂​​质和电荷,有助于形成 ap+ -n +隧道结。使用电子全息术在再生界面处的静电势分布进一步证实了这一假设。研究了新的蚀刻技术以改善再生长界面。结果表明,低功率干法刻蚀显着降低了再生 pn 结的界面电荷和反向漏电流。发现光电化学湿蚀刻可有效减少再生长界面附近的深能级缺陷。原子层蚀刻使用自限性化学工艺,从而去除损坏的层而不会引起进一步的蚀刻损坏。基于叔丁基氯的原位蚀刻可以作为干蚀刻的替代蚀刻方法,具有减少的蚀刻损伤。在器件方面,展示了具有低泄漏电流的再生 pn 结和垂直结场效应晶体管。通过表面处理和低损伤蚀刻使用再生长优化和再生长界面工程,可以预期选择性区域再生长和相关器件的进一步改进。这些结果代表了实现高性能 GaN 电力电子器件和系统的选择性区域再生长和掺杂的重要一步。

更新日期:2021-05-26
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