Research on the critical thickness of Al<sub>0.2</sub>Ga<sub>0.8</sub>N template grown on AlN/sapphire substrate

Yaqin Li; Jianping Liu; Aiqin Tian; Masao Ikeda; Wei Zhou; Hui Yang

doi:10.1088/1674-4926/26030007

J. Semicond. > In Press

ARTICLES

Research on the critical thickness of Al_0.2Ga_0.8N template grown on AlN/sapphire substrate

Yaqin Li^{1, 2, 3}, Jianping Liu^{1, 2, 3,}, Aiqin Tian^{2, 3,}, Masao Ikeda^{2, 3}, Wei Zhou^{2, 3} and Hui Yang^{1, 2, 3}

+ Author Affiliations

Corresponding author: Jianping Liu, jpliu2010@sinano.ac.cn; Aiqin Tian, aqtian2012@sinano.ac.cn

DOI: 10.1088/1674-4926/26030007CSTR: 32376.14.1674-4926.26030007

Abstract: AlGaN-based ultraviolet (UV) laser diodes (LDs), with emission wavelength in the 280–365 nm range, are promising for applications in medical diagnostics and biological sensing, making them a prominent research focus in both academia and industry in recent years. A key challenge in their development is the large stress induced during the epitaxial growth of LD structures, which arises from the lack of lattice-matched substrates, and severely degrades the quantum efficiency and overall LD performance. This study presents an in-depth investigation into the growth mode and stress evolution of thick Al_0.2Ga_0.8N template. Firstly, we used the compressive stress between the Al_0.2Ga_0.8N layer and AlN/Sapphire substrate to form spontaneously three-dimensional growth to annihilate dislocations. Secondly, based on the Nakajima's theory of elasticity, we refined the conventional theoretical models for AlGaN strain relaxation of the S–K growth mode and critical thickness by considering the crucial role of threading dislocations (TDs) in releasing compressive stress. The experimentally measured critical thickness for three-dimensional growth was consistent with the calculated results. Furthermore, a crack-free high-quality 5 μm-thick Al_0.2Ga_0.8N template was successfully grown on an AlN/sapphire substrate.

Keywords: ultraviolet lasers, strain relaxation, critical thickness

References

[1]	Kneissl M, Rass J. III-nitride ultraviolet emitters: Technology and applications. Cham: Springer International Publishing, 2016
[2]	Hargis P J Jr, Sobering T J, Tisone G C, et al. Ultraviolet fluorescence identification of protein, DNA, and bacteria. Opt Instrum Gas Emiss Monit Atmos Meas, 1995, 2366: 147 doi: 10.1117/12.205554
[3]	Xie N, Xu F J, Wang J M, et al. Stress evolution in AlN growth on nano-patterned sapphire substrates. Appl Phys Express, 2020, 13(1): 015504 doi: 10.7567/1882-0786/ab582c
[4]	Hagedorn S, Mogilatenko A, Walde S, et al. High-temperature annealing and patterned AlN/sapphire interfaces. Phys Status Solidi B, 2021, 258(10): 2100187 doi: 10.1002/pssb.202100187
[5]	Uesugi K, Miyake H. Fabrication of AlN templates by high-temperature face-to-face annealing for deep UV LEDs. Jpn J Appl Phys, 2021, 60(12): 120502 doi: 10.35848/1347-4065/ac3026
[6]	Uesugi K, Kuboya S, Shojiki K, et al. 263 nm wavelength UV-C LED on face-to-face annealed sputter-deposited AlN with low screw- and mixed-type dislocation densities. Appl Phys Express, 2022, 15(5): 055501 doi: 10.35848/1882-0786/ac66c2
[7]	Lu S P, Ben J W, Jiang K, et al. 6-inch AlN epitaxial films with low dislocation densities via MOCVD. J Semicond, 2025, 46(2): 022501 doi: 10.1088/1674-4926/24110030
[8]	Amano H, Collazo R, De Santi C, et al. The 2020 UV emitter roadmap. J Phys D: Appl Phys, 2020, 53(50): 503001 doi: 10.1088/1361-6463/aba64c
[9]	Bryan I, Bryan Z, Mita S, et al. The role of surface kinetics on composition and quality of AlGaN. J Cryst Growth, 2016, 451: 65 doi: 10.1016/j.jcrysgro.2016.06.055
[10]	Sato K, Yasue S, Yamada K, et al. Room-temperature operation of AlGaN ultraviolet-B laser diode at 298 nm on lattice-relaxed Al_0.6Ga_0.4N/AlN/sapphire. Appl Phys Express, 2020, 13(3): 031004
[11]	Fischer A, Kühne H, Richter H. New approach in equilibrium theory for strained layer relaxation. Phys Rev Lett, 1994, 73(20): 2712 doi: 10.1103/PhysRevLett.73.2712
[12]	Orr B G, Kessler D, Snyder C W, et al. A model for strain-induced roughening and coherent island growth. Europhys Lett, 1992, 19(1): 33 doi: 10.1209/0295-5075/19/1/006
[13]	Frank F C, van der Merwe J H. One-dimensional dislocations. I. static theory. Proc R Soc Lond Ser A Math Phys Sci, 1949, 198(1053): 205
[14]	Volmer M. Nucleus formation in supersaturated systems. Zeitschrift für Physikalische Chemie, 1926, 119: 277
[15]	Stranski I N, Krastanov L. Theory of orientation separation of ionic crystals. Akad Wiss Let Mainz Math Natur Kl IIb, 1939, 146: 797
[16]	Nakajima K, Ujihara T, Miyashita S, et al. Effects of misfit dislocations and AlN buffer layer on the GaInN/GaN phase diagram of the growth mode. J Appl Phys, 2001, 89(1): 146 doi: 10.1063/1.1330247
[17]	Zhao W, Wang L, Wang J X, et al. Theoretical study on critical thicknesses of InGaN grown on (0001) GaN. J Cryst Growth, 2011, 327(1): 202 doi: 10.1016/j.jcrysgro.2011.05.002
[18]	Harutyunyan V S, Aivazyan A P, Weber E R, et al. High-resolution X-ray diffraction strain-stress analysis of GaN/sapphire heterostructures. J Phys D: Appl Phys, 2001, 34(10A): A35 doi: 10.1088/0022-3727/34/10A/308
[19]	Huang S Y, Yang J R. A transmission electron microscopy observation of dislocations in GaN grown on (0001) sapphire by metal organic chemical vapor deposition. Jpn J Appl Phys, 2008, 47(10R): 7998 doi: 10.1143/JJAP.47.7998
[20]	Nakajima K. Equilibrium phase diagrams for stranski-krastanov structure mode of III–V ternary quantum dots. Jpn J Appl Phys, 1999, 38(4R): 1875 doi: 10.1143/JJAP.38.1875
[21]	Mohamad R, Béré A, Hounkpati V, et al. A theoretical investigation of the miscibility and structural properties of In_xAl_yGa_1−x−yN alloys. Phys Status Solidi B, 2018, 255(5): 1700394 doi: 10.1002/pssb.201700394
[22]	Vurgaftman I, Meyer J R. Band parameters for nitrogen-containing semiconductors. J Appl Phys, 2003, 94(6): 3675 doi: 10.1063/1.1600519
[23]	Sohi P, Martin D, Grandjean N. Critical thickness of GaN on AlN: Impact of growth temperature and dislocation density. Semicond Sci Technol, 2017, 32(7): 075010 doi: 10.1088/1361-6641/aa7248
[24]	Li Y Q, Tian A Q, Liu J P, et al. Two-step growth of crack-free 5 μm-thick Al_0.2Ga_0.8N on sapphire substrate with sputtered AlN nucleation layer. J Appl Phys, 2025, 137(6): 065703 doi: 10.1063/5.0249836
[25]	Iwaya M, Tanaka S, Omori T, et al. Recent development of UV-B laser diodes. Jpn J Appl Phys, 2022, 61(4): 040501 doi: 10.35848/1347-4065/ac3be8

Fig. 1. (Color online) Measurement results of reflectance intensities by in situ observation of 5 μm Al_0.2Ga_0.8N using Two-step growth method.

DownLoad: Full-Size Img PowerPoint

Fig. 2. (Color online) Cross-section TEM images of Al_0.2Ga_0.8N.

DownLoad: Full-Size Img PowerPoint

Fig. 3. (Color online) Critical thicknesses of 3D growth versus Al-content of AlGaN with different density of dislocation.

DownLoad: Full-Size Img PowerPoint

Fig. 4. (Color online) (a) FWHM values of (0002) and (10-12) measured by X-ray rocking curves for the 5 μm Al_0.2Ga_0.8N using two-step growth method. (b) Relation between AlN molar fraction and dislocation density of AlGaN with a film thickness of over 1 μm.

DownLoad: Full-Size Img PowerPoint

Table 1. Parameters used in calculation.

Parameter		AlN	GaN
Lateral lattice constant of a (nm)		0.3112	0.3189
Young’s modulus ${Y} $ (GPa)		340	329
Elastic constants C_ij	C₁₁/GPa	396	390
	C₁₂/GPa	137	145
	C₁₃/GPa	108	106
	C₃₃/GPa	373	398

DownLoad: CSV

[1]	Kneissl M, Rass J. III-nitride ultraviolet emitters: Technology and applications. Cham: Springer International Publishing, 2016
[2]	Hargis P J Jr, Sobering T J, Tisone G C, et al. Ultraviolet fluorescence identification of protein, DNA, and bacteria. Opt Instrum Gas Emiss Monit Atmos Meas, 1995, 2366: 147 doi: 10.1117/12.205554
[3]	Xie N, Xu F J, Wang J M, et al. Stress evolution in AlN growth on nano-patterned sapphire substrates. Appl Phys Express, 2020, 13(1): 015504 doi: 10.7567/1882-0786/ab582c
[4]	Hagedorn S, Mogilatenko A, Walde S, et al. High-temperature annealing and patterned AlN/sapphire interfaces. Phys Status Solidi B, 2021, 258(10): 2100187 doi: 10.1002/pssb.202100187
[5]	Uesugi K, Miyake H. Fabrication of AlN templates by high-temperature face-to-face annealing for deep UV LEDs. Jpn J Appl Phys, 2021, 60(12): 120502 doi: 10.35848/1347-4065/ac3026
[6]	Uesugi K, Kuboya S, Shojiki K, et al. 263 nm wavelength UV-C LED on face-to-face annealed sputter-deposited AlN with low screw- and mixed-type dislocation densities. Appl Phys Express, 2022, 15(5): 055501 doi: 10.35848/1882-0786/ac66c2
[7]	Lu S P, Ben J W, Jiang K, et al. 6-inch AlN epitaxial films with low dislocation densities via MOCVD. J Semicond, 2025, 46(2): 022501 doi: 10.1088/1674-4926/24110030
[8]	Amano H, Collazo R, De Santi C, et al. The 2020 UV emitter roadmap. J Phys D: Appl Phys, 2020, 53(50): 503001 doi: 10.1088/1361-6463/aba64c
[9]	Bryan I, Bryan Z, Mita S, et al. The role of surface kinetics on composition and quality of AlGaN. J Cryst Growth, 2016, 451: 65 doi: 10.1016/j.jcrysgro.2016.06.055
[10]	Sato K, Yasue S, Yamada K, et al. Room-temperature operation of AlGaN ultraviolet-B laser diode at 298 nm on lattice-relaxed Al_0.6Ga_0.4N/AlN/sapphire. Appl Phys Express, 2020, 13(3): 031004
[11]	Fischer A, Kühne H, Richter H. New approach in equilibrium theory for strained layer relaxation. Phys Rev Lett, 1994, 73(20): 2712 doi: 10.1103/PhysRevLett.73.2712
[12]	Orr B G, Kessler D, Snyder C W, et al. A model for strain-induced roughening and coherent island growth. Europhys Lett, 1992, 19(1): 33 doi: 10.1209/0295-5075/19/1/006
[13]	Frank F C, van der Merwe J H. One-dimensional dislocations. I. static theory. Proc R Soc Lond Ser A Math Phys Sci, 1949, 198(1053): 205
[14]	Volmer M. Nucleus formation in supersaturated systems. Zeitschrift für Physikalische Chemie, 1926, 119: 277
[15]	Stranski I N, Krastanov L. Theory of orientation separation of ionic crystals. Akad Wiss Let Mainz Math Natur Kl IIb, 1939, 146: 797
[16]	Nakajima K, Ujihara T, Miyashita S, et al. Effects of misfit dislocations and AlN buffer layer on the GaInN/GaN phase diagram of the growth mode. J Appl Phys, 2001, 89(1): 146 doi: 10.1063/1.1330247
[17]	Zhao W, Wang L, Wang J X, et al. Theoretical study on critical thicknesses of InGaN grown on (0001) GaN. J Cryst Growth, 2011, 327(1): 202 doi: 10.1016/j.jcrysgro.2011.05.002
[18]	Harutyunyan V S, Aivazyan A P, Weber E R, et al. High-resolution X-ray diffraction strain-stress analysis of GaN/sapphire heterostructures. J Phys D: Appl Phys, 2001, 34(10A): A35 doi: 10.1088/0022-3727/34/10A/308
[19]	Huang S Y, Yang J R. A transmission electron microscopy observation of dislocations in GaN grown on (0001) sapphire by metal organic chemical vapor deposition. Jpn J Appl Phys, 2008, 47(10R): 7998 doi: 10.1143/JJAP.47.7998
[20]	Nakajima K. Equilibrium phase diagrams for stranski-krastanov structure mode of III–V ternary quantum dots. Jpn J Appl Phys, 1999, 38(4R): 1875 doi: 10.1143/JJAP.38.1875
[21]	Mohamad R, Béré A, Hounkpati V, et al. A theoretical investigation of the miscibility and structural properties of In_xAl_yGa_1−x−yN alloys. Phys Status Solidi B, 2018, 255(5): 1700394 doi: 10.1002/pssb.201700394
[22]	Vurgaftman I, Meyer J R. Band parameters for nitrogen-containing semiconductors. J Appl Phys, 2003, 94(6): 3675 doi: 10.1063/1.1600519
[23]	Sohi P, Martin D, Grandjean N. Critical thickness of GaN on AlN: Impact of growth temperature and dislocation density. Semicond Sci Technol, 2017, 32(7): 075010 doi: 10.1088/1361-6641/aa7248
[24]	Li Y Q, Tian A Q, Liu J P, et al. Two-step growth of crack-free 5 μm-thick Al_0.2Ga_0.8N on sapphire substrate with sputtered AlN nucleation layer. J Appl Phys, 2025, 137(6): 065703 doi: 10.1063/5.0249836
[25]	Iwaya M, Tanaka S, Omori T, et al. Recent development of UV-B laser diodes. Jpn J Appl Phys, 2022, 61(4): 040501 doi: 10.35848/1347-4065/ac3be8

26030007_Supplementary Information.pdf

Search

GET CITATION

shu

Export: BibTex EndNote

Article Metrics

Article views: 242 Times PDF downloads: 90 Times Cited by: 0 Times

History

Received: 27 April 2026 Revised: 03 May 2026 Online: Accepted Manuscript: 03 June 2026Uncorrected proof: 07 August 2026

Article Navigation > Journal of Semiconductors > 2026 > Uncorrected proof

Yaqin Li, Jianping Liu, Aiqin Tian, Masao Ikeda, Wei Zhou, Hui Yang. Research on the critical thickness of Al0.2Ga0.8N template grown on AlN/sapphire substrate[J]. Journal of Semiconductors, 2026, In Press. doi: 10.1088/1674-4926/26030007 ****Y Q Li, J P Liu, A Q Tian, M Ikeda, W Zhou, and H Yang, Research on the critical thickness of Al0.2Ga0.8N template grown on AlN/sapphire substrate[J]. J. Semicond., 2026, accepted doi: 10.1088/1674-4926/26030007

Citation:

Yaqin Li, Jianping Liu, Aiqin Tian, Masao Ikeda, Wei Zhou, Hui Yang. Research on the critical thickness of Al_0.2Ga_0.8N template grown on AlN/sapphire substrate[J]. Journal of Semiconductors, 2026, In Press. doi: 10.1088/1674-4926/26030007 ****

Y Q Li, J P Liu, A Q Tian, M Ikeda, W Zhou, and H Yang, Research on the critical thickness of Al_0.2Ga_0.8N template grown on AlN/sapphire substrate[J]. J. Semicond., 2026, accepted doi: 10.1088/1674-4926/26030007

Citation:

PDF( 3520 KB)

Research on the critical thickness of Al_0.2Ga_0.8N template grown on AlN/sapphire substrate

DOI: 10.1088/1674-4926/26030007

CSTR: 32376.14.1674-4926.26030007

Yaqin Li^{1, 2, 3},
Jianping Liu^{1, 2, 3,},
Aiqin Tian^{2, 3,},
Masao Ikeda^{2, 3},
Wei Zhou^{2, 3},
Hui Yang^{1, 2, 3}

1.
School of Nano-Tech and Nano-Bionics, University of Science and Technology of China, Hefei 230026, China
2.
Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
3.
Key Laboratory of Semiconductor Display Materials and Chips, Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China

More Information

Yaqin Li got her bachelor’s degree in 2016 from Hebei University of Technology. Now she is a doctoral student at University of Science and Technology of China under the supervision of Prof. Jianping Liu. Her research focuses on MOCVD growth and GaN-based laser diodes
Jianping Liu got his doctoral degree in 2004 from Institute of Semiconductors, Chinese Academy of Sciences. He is currently a Professor with the Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences. His current research interests include GaN-based materials and devices, and MOCVD technology
Aiqin Tian got her doctoral degree in 2017 from University of Chinese Academy of Sciences. She is currently a Professor with the Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences. Her research focuses on GaN-based optoelectronic materials and devices
Corresponding author: jpliu2010@sinano.ac.cn; aqtian2012@sinano.ac.cn
Received Date: 2026-04-27
Revised Date: 2026-05-03

Available Online: 2026-06-03

Abstract

Abstract

AlGaN-based ultraviolet (UV) laser diodes (LDs), with emission wavelength in the 280–365 nm range, are promising for applications in medical diagnostics and biological sensing, making them a prominent research focus in both academia and industry in recent years. A key challenge in their development is the large stress induced during the epitaxial growth of LD structures, which arises from the lack of lattice-matched substrates, and severely degrades the quantum efficiency and overall LD performance. This study presents an in-depth investigation into the growth mode and stress evolution of thick Al_0.2Ga_0.8N template. Firstly, we used the compressive stress between the Al_0.2Ga_0.8N layer and AlN/Sapphire substrate to form spontaneously three-dimensional growth to annihilate dislocations. Secondly, based on the Nakajima's theory of elasticity, we refined the conventional theoretical models for AlGaN strain relaxation of the S–K growth mode and critical thickness by considering the crucial role of threading dislocations (TDs) in releasing compressive stress. The experimentally measured critical thickness for three-dimensional growth was consistent with the calculated results. Furthermore, a crack-free high-quality 5 μm-thick Al_0.2Ga_0.8N template was successfully grown on an AlN/sapphire substrate.
- ultraviolet lasers,
- strain relaxation,
- critical thickness

Supplementary materials to this article can be found online at https://doi.org/10.1088/1674-4926/26030007.

FullText(HTML)

References(25)