J. Semicond. > 2024, Volume 45 > Issue 2 > 021501, doi: 10.1088/1674-4926/45/2/021501
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REVIEWS

Progress in efficient doping of Al-rich AlGaN

Jiaming Wang1, Fujun Xu1, , Lisheng Zhang1, 2, Jing Lang1, Xuzhou Fang1, Ziyao Zhang1, Xueqi Guo1, Chen Ji1, Chengzhi Ji1, Fuyun Tan1, Xuelin Yang1, Xiangning Kang1, Zhixin Qin1, 2, Ning Tang1, 3, 4, Xinqiang Wang1, 3, 4, Weikun Ge1 and Bo Shen1, 3, 4,

+ Author Affiliations

 Corresponding author: Fujun Xu, fjxu@pku.edu.cn; Bo Shen, bshen@pku.edu.cn

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Abstract: The development of semiconductors is always accompanied by the progress in controllable doping techniques. Taking AlGaN-based ultraviolet (UV) emitters as an example, despite a peak wall-plug efficiency of 15.3% at the wavelength of 275 nm, there is still a huge gap in comparison with GaN-based visible light-emitting diodes (LEDs), mainly attributed to the inefficient doping of AlGaN with increase of the Al composition. First, p-doping of Al-rich AlGaN is a long-standing challenge and the low hole concentration seriously restricts the carrier injection efficiency. Although p-GaN cladding layers are widely adopted as a compromise, the high injection barrier of holes as well as the inevitable loss of light extraction cannot be neglected. While in terms of n-doping the main issue is the degradation of the electrical property when the Al composition exceeds 80%, resulting in a low electrical efficiency in sub-250 nm UV-LEDs. This review summarizes the recent advances and outlines the major challenges in the efficient doping of Al-rich AlGaN, meanwhile the corresponding approaches pursued to overcome the doping issues are discussed in detail.

Key words: AlGaN-based UV-LEDs, Al-rich AlGaN, doping



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Fig. 1.  (Color online) State of the art of UV-LEDs in the wavelength of 210−320 nm. The wall-plug efficiency values are plotted as reported or calculated from reported voltage, current, and light output power. Data obtained from Refs. [9, 16−47].

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Fig. 2.  (Color online) (a) Schematic band diagram and carrier injection in AlGaN-based UV-LEDs. (b) Equivalent circuit diagram for AlGaN-based UV-LEDs with the flip-chip configuration. The voltage drops are estimated under the current densities of 50−100 A/cm2 [12].

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Fig. 3.  (Color online) State of the art of (a) conductivity and (b) electron concentration in n-doped Al-rich AlGaN. Data obtained from Refs. [50, 52−65, 70, 74−76].

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Fig. 4.  (Color online) Theoretical formation energy change of (a) VⅢ and (b) CN as a function of Ⅴ/Ⅲ ratio and growth rate (proportional to the metalorganic flow)[52]. Experimental trade-off of the (c) growth temperature and (d) Ⅴ/Ⅲ ratio to suppress the formation of VⅢ-nSi and CN[53].

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Fig. 5.  (Color online) (a) Conductivity and (b) electron concentration as a function of Si concentration in n-Al0.7Ga0.3N[59].

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Fig. 6.  (Color online) (a) The activation energy of Si in Al-rich AlGaN with Al composition higher than 80%[66]. (b) Configuration coordinate diagram of the DX center in Si-doped Al(Ga)N[74].

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Fig. 7.  (Color online) (a) Activation energy of Mg in dependence of Al composition in AlGaN. Data obtained from Refs. [9, 79−87]. (b) Formation enthalpies of MgGa/MgAl as a function of Al composition in bulk AlGaN under N-rich growth condition[88].

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Fig. 8.  (Color online) (a) Schematic illustration of valence band for p-type superlattice (SL) doping[92]. (b) The vertical miniband transport of holes in Al0.63Ga0.37N/Al0.46Ga0.54N SLs with a constant barrier thickness of 0.75 nm[96].

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Fig. 9.  (Color online) (a) Schematic illustration of polarization-induced p-type doping in graded polar heterostructures[79]. (b) Directions of the spontaneous and piezoelectric polarization in strained N-polar AlGaN/GaN and Al-polar AlGaN/AlN heterostructures[98].

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Fig. 10.  (Color online) (a) Formation enthalpies of MgGa/MgAl as a function of Al composition on the surface of AlGaN under N-rich growth condition[88]. (b) Schematic diagram of the Mg-rich profiles by periodic interruptions of Al and Ga source during growth[88].

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    Received: 22 August 2023 Revised: 16 September 2023 Online: Accepted Manuscript: 03 November 2023Uncorrected proof: 08 December 2023Published: 10 February 2024

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      Article Navigation >  Journal of Semiconductors  > 2024  >  45(2): 021501
      Jiaming Wang, Fujun Xu, Lisheng Zhang, Jing Lang, Xuzhou Fang, Ziyao Zhang, Xueqi Guo, Chen Ji, Chengzhi Ji, Fuyun Tan, Xuelin Yang, Xiangning Kang, Zhixin Qin, Ning Tang, Xinqiang Wang, Weikun Ge, Bo Shen. Progress in efficient doping of Al-rich AlGaN[J]. Journal of Semiconductors, 2024, 45(2): 021501. doi: 10.1088/1674-4926/45/2/021501 J M Wang, F J Xu, L S Zhang, J Lang, X Z Fang, Z Y Zhang, X Q Guo, C Ji, C Z Ji, F Y Tan, X L Yang, X N Kang, Z X Qin, N Tang, X Q Wang, W K Ge, B Shen. Progress in efficient doping of Al-rich AlGaN[J]. J. Semicond, 2024, 45(2): 021501. doi: 10.1088/1674-4926/45/2/021501Export: BibTex EndNote
      Citation:
      Jiaming Wang, Fujun Xu, Lisheng Zhang, Jing Lang, Xuzhou Fang, Ziyao Zhang, Xueqi Guo, Chen Ji, Chengzhi Ji, Fuyun Tan, Xuelin Yang, Xiangning Kang, Zhixin Qin, Ning Tang, Xinqiang Wang, Weikun Ge, Bo Shen. Progress in efficient doping of Al-rich AlGaN[J]. Journal of Semiconductors, 2024, 45(2): 021501. doi: 10.1088/1674-4926/45/2/021501

      J M Wang, F J Xu, L S Zhang, J Lang, X Z Fang, Z Y Zhang, X Q Guo, C Ji, C Z Ji, F Y Tan, X L Yang, X N Kang, Z X Qin, N Tang, X Q Wang, W K Ge, B Shen. Progress in efficient doping of Al-rich AlGaN[J]. J. Semicond, 2024, 45(2): 021501. doi: 10.1088/1674-4926/45/2/021501
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      Progress in efficient doping of Al-rich AlGaN

      doi: 10.1088/1674-4926/45/2/021501
      • 1.

        State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China

      • 2.

        Beijing SinoGaN Semiconductor Technology Co., Ltd., Beijing 101399, China

      • 3.

        Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing 100871, China

      • 4.

        Collaborative Innovation Center of Quantum Matter, Beijing 100871, China

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      • Author Bio:

        Jiaming Wang Jiaming Wang is a postdoc at the School of Physics at Peking University. He received his Ph.D. degree from Peking University in 2015. His current research mainly focuses on AlGaN-based DUV-LEDs

        Fujun Xu Fujun Xu is an associate professor in the School of Physics at Peking University. He received his Ph.D. degree from Peking University in 2008. His current research mainly focuses on AlGaN-based DUV-related materials and devices

        Bo Shen Bo Shen is a professor in the School of Physics at Peking University. He received his M.S. and Ph.D. degrees from University of Science and Technology of China, and Tohoku University Japan, respectively. His current research mainly focuses on wide bandgap semiconductor materials and devices

      • Corresponding author: fjxu@pku.edu.cn; bshen@pku.edu.cn
      • Received Date: 2023-08-22
      • Revised Date: 2023-09-16
        • Available Online: 2023-11-03

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