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High-quality AlGaN epitaxial structures and realization of UVC vertical-cavity surface-emitting lasers

高质量的AlGaN外延结构和UVC垂直腔面发射激光 器的实现

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Abstract

AlGaN-based vertical-cavity surface-emitting lasers (VCSELs) have garnered recent interest due to their superior material properties and device benefits. Nevertheless, AlGaN-based VCSELs are extremely difficult to realize due to numerous technical limitations associated with both material epitaxial growth and chip fabrication. This study fabricated a high-quality AlGaN multiple quantum wells (MQWs) structure using epitaxial lateral overgrowth and analyzed it using X-ray diffraction (XRD) and photoluminescence (PL) measurements. With an edge dislocation density (DD) of 109 cm−2, XRD measurements reveal that the AlN template is nearly fully relaxed. The subsequent AlGaN/AlN superlattice (SL) layer is introduced to decrease the edge DD, and the edge DD in the MQWs is ∼108 cm−2. According to PL measurements, the internal quantum efficiency of the MQWs is as high as 62%, and radiative recombination dominated the emission of the MQWs at room temperature. Using these epitaxial wafers, ultraviolet radiation C (UVC) VCSELs were fabricated using various techniques, including laser lift-off (LLO) and chemical mechanical polishing (CMP). The crystallinity of the MQWs was unaffected by sapphire substrate removal using LLO. After removing the sapphire substrate using LLO and CMP, UVC surface-stimulated emission was observed in MQWs. AlGaN-based UVC VCSELs with lasing wavelengths of 275.91, 276.28, and 277.64 nm have been fabricated. The minimum threshold for UVC VCSELs is 0.79 MW cm−2, which is a record low.

摘要

AlGaN基垂直腔面发射激光器(VCSEL)因其优越的材料性质和 器件优点吸引了很多关注. 然而, 由于材料外延生长和器件制备工艺的 局限, AlGaN基VCSEL制备很困难. 本工作通过侧向外延生长技术制备 了高质量的AlGaN多量子阱(MQWs)结构的外延片, 并通过X射线衍射 (XRD)和光致发光(PL)实验对外延片进行了分析. XRD测量显示, 外延 片中的AlN模板层几乎是弛豫的, 刃位错密度为109 cm−2. 随后, 生长的 AlGaN/AlN超晶格(SL)层被用来减少刃位错密度, 使得量子阱中的位错 密度为108 cm−2. 根据PL测试结果, MQWs的内量子效率(IQE)为62%, 且在室温下的发光以辐射复合为主. 通过激光剥离(LLO)和化学机械抛 光(CMP)技术, 将这些外延片制备成UVC VCSEL. 经过这些工艺, MQWs的晶体质量没有受到影响, 还在抛光之后的表面观察到了UVC 波段的受激辐射. 这些AlGaN基UVC VCSEL在275.91, 276.28和 277.64 nm实现了激射, 最小激射阈值为0.79 MW cm−2.

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Acknowledgements

This work was supported by the National Key Research and Development Program of China (2017YFE0131500) and the National Natural Science Foundation of China (62104204 and U21A20493).

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Authors and Affiliations

  1. Department of Electronic Engineering, Optoelectronics Engineering Research Center, School of Electronic Science and Engineering (National Model Microelectronics College), Xiamen University, Xiamen, 361005, China

    Zhongming Zheng  (郑重明), Yukun Wang  (王玉坤), Yang Mei  (梅洋), Hao Long  (龙浩), Leiying Ying  (应磊莹), Zhiwei Zheng  (郑志威) & Baoping Zhang  (张保平)

  2. Advanced Micro-Fabrication Equipment Inc., Shanghai, 201201, China

    Jason Hoo  (胡建正) & Shiping Guo  (郭世平)

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  1. Zhongming Zheng  (郑重明)
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  3. Jason Hoo  (胡建正)
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  4. Shiping Guo  (郭世平)
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Contributions

Zheng Z fabricated the devices, measured the devices and epilayers, and wrote the manuscript. Hoo J grew the epitaxial structures and helped to measure the epilayers. Zhang B proposed the outline of the manuscript and revised the manuscript. Guo S helped to revise the manuscript. All the authors contributed to the discussion of the work.

Corresponding authors

Correspondence to Shiping Guo  (郭世平) or Baoping Zhang  (张保平).

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Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary information

Experimental details and supporting data are available in the online version of the paper.

Zhongming Zheng is a postdoctoral researcher at Xiamen University. He earned his PhD degree from Xiamen University in 2021. His research focuses on III-nitride materials and devices.

Shiping Guo received his PhD degree in semiconductor physics and device physics from Shanghai Institute of Technical Physics, Chinese Academy of Sciences, in 1994. Currently, he serves as Group Vice President and General Manager of MOCVD Product Division at AMEC. His research interests include MOCVD hardware development, project management and epitaxial growth process development of III-N based materials and devices. Before AMEC, he worked at IQR RF LLC and EMCORE Corp. from 2001 to 2012 and at several research groups at the City University of New York, Tohoku University and Shanghai Institute of Technical Physics.

Baoping Zhang was born in Hebei, China, in 1963. He received the BS degree in physics from Lanzhou University, Lanzhou, China, in 1983, the ME degree in microelectronics from Hebei Semiconductor Research Institute, Shijiazhuang, China, and the Dr. Eng. degree in applied physics from the University of Tokyo, Tokyo, Japan, in 1994. He is currently a distinguished professor at the School of Electronic Science and Engineering, Xiamen University, China, where he is engaged in wide-gap semiconductor materials and devices, especially GaN-based light-emitting diodes (LEDs) and VCSELs.

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Zheng, Z., Wang, Y., Hoo, J. et al. High-quality AlGaN epitaxial structures and realization of UVC vertical-cavity surface-emitting lasers. Sci. China Mater. 66, 1978–1988 (2023). https://doi.org/10.1007/s40843-022-2310-5

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