Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD

Ghosh, Saptarsi; Hinz, Alexander M; Frentrup, Martin; Alam, Saiful; Wallis, David J; Oliver, Rachel A

doi:10.1088/1361-6641/acb9b6

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Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD

Saptarsi Ghosh

, Alexander M Hinz

, Martin Frentrup, Saiful Alam, David J Wallis, Rachel A Oliver

Semiconductor Science and Technology, Volume: 38, Issue: 4, Start page: 044001

Swansea University Author: Saptarsi Ghosh

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DOI (Published version): 10.1088/1361-6641/acb9b6

Abstract

For the growth of low-defect crack-free GaN heterostructures on large-area silicon substrates, compositional grading of AlGaN is a widely adapted buffer technique to restrict the propagation of lattice-mismatch induced defects and balance the thermal expansion mismatch-induced tensile stress. So far...

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Published in:	Semiconductor Science and Technology
ISSN:	0268-1242 1361-6641
Published:	IOP Publishing 2023
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URI:	https://cronfa.swan.ac.uk/Record/cronfa66871
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So far, a consolidation of the design strategy of such step-graded buffers has been impaired by the incomplete understanding of the effect of individual buffer design parameters on the mechanical and microstructural properties of the epilayers. Herein, we have analyzed a series of metal-organic chemical vapor deposition grown GaN/graded-AlGaN/AlN/Si heterostructures through in situ curvature measurements and post-growth x-ray diffraction (XRD). Our results reveal that in such epi structures, the GaN layer itself induces more compressive stress than the AlGaN buffer, but the underlying AlGaN layers dictate the magnitude of this stress. Furthermore, for a fixed AlGaN buffer thickness, the mean-stress accumulated during the GaN growth is found to be correlated with its structural properties. Specifically, one µm thick GaN layers that acquire 1.50 GPa or higher compressive mean-stress are seen to possess XRD ω-FWHM values less than 650 arc-sec. Also, the evolution of instantaneous stresses during the growth of the AlGaN layers is found to be a valuable indicator for buffer optimization, and composition difference between successive layers is established as a crucial criterion. The results also show that increasing the total buffer thickness (for a fixed number of steps) or increasing the number of steps (for a fixed total buffer thickness) may not always be beneficial. Irrespective of the buffer thickness, optimized high electron mobility transistor structures show similarly low sheet-resistance (∼350 Ω □)−1 and high mobility (∼2000 cm2 V−1 s −1) at room temperature.</abstract><type>Journal Article</type><journal>Semiconductor Science and Technology</journal><volume>38</volume><journalNumber>4</journalNumber><paginationStart>044001</paginationStart><paginationEnd/><publisher>IOP Publishing</publisher><placeOfPublication/><isbnPrint/><isbnElectronic/><issnPrint>0268-1242</issnPrint><issnElectronic>1361-6641</issnElectronic><keywords>GaN-on-Si, AlGaN buffer, MOCVD, heteroepitaxy</keywords><publishedDay>1</publishedDay><publishedMonth>4</publishedMonth><publishedYear>2023</publishedYear><publishedDate>2023-04-01</publishedDate><doi>10.1088/1361-6641/acb9b6</doi><url/><notes/><college>COLLEGE NANME</college><department>Aerospace, Civil, Electrical, and Mechanical Engineering</department><CollegeCode>COLLEGE CODE</CollegeCode><DepartmentCode>ACEM</DepartmentCode><institution>Swansea University</institution><apcterm/><funders>This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) under the grant ‘Hetero-print’: A holistic approach to transfer-printing for heterogeneous integration in manufacturing (EP/R03480X/1). Alexander M Hinz acknowledges the Deutsche Forschungsgemeinschaft for his Research Fellowship at the University of Cambridge. David J Wallis acknowledges the support of the EPSRCfellowship (EP/N01202X/2). The authors are grateful to Dr Menno J Kappers and Dr Gunnar Kusch for their critical suggestions. 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spelling	v2 66871 2024-06-23 Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD 3e247ecabd6eddd319264d066b0ce959 0000-0003-1685-6228 Saptarsi Ghosh Saptarsi Ghosh true false 2024-06-23 ACEM For the growth of low-defect crack-free GaN heterostructures on large-area silicon substrates, compositional grading of AlGaN is a widely adapted buffer technique to restrict the propagation of lattice-mismatch induced defects and balance the thermal expansion mismatch-induced tensile stress. So far, a consolidation of the design strategy of such step-graded buffers has been impaired by the incomplete understanding of the effect of individual buffer design parameters on the mechanical and microstructural properties of the epilayers. Herein, we have analyzed a series of metal-organic chemical vapor deposition grown GaN/graded-AlGaN/AlN/Si heterostructures through in situ curvature measurements and post-growth x-ray diffraction (XRD). Our results reveal that in such epi structures, the GaN layer itself induces more compressive stress than the AlGaN buffer, but the underlying AlGaN layers dictate the magnitude of this stress. Furthermore, for a fixed AlGaN buffer thickness, the mean-stress accumulated during the GaN growth is found to be correlated with its structural properties. Specifically, one µm thick GaN layers that acquire 1.50 GPa or higher compressive mean-stress are seen to possess XRD ω-FWHM values less than 650 arc-sec. Also, the evolution of instantaneous stresses during the growth of the AlGaN layers is found to be a valuable indicator for buffer optimization, and composition difference between successive layers is established as a crucial criterion. The results also show that increasing the total buffer thickness (for a fixed number of steps) or increasing the number of steps (for a fixed total buffer thickness) may not always be beneficial. Irrespective of the buffer thickness, optimized high electron mobility transistor structures show similarly low sheet-resistance (∼350 Ω □)−1 and high mobility (∼2000 cm2 V−1 s −1) at room temperature. Journal Article Semiconductor Science and Technology 38 4 044001 IOP Publishing 0268-1242 1361-6641 GaN-on-Si, AlGaN buffer, MOCVD, heteroepitaxy 1 4 2023 2023-04-01 10.1088/1361-6641/acb9b6 COLLEGE NANME Aerospace, Civil, Electrical, and Mechanical Engineering COLLEGE CODE ACEM Swansea University This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) under the grant ‘Hetero-print’: A holistic approach to transfer-printing for heterogeneous integration in manufacturing (EP/R03480X/1). Alexander M Hinz acknowledges the Deutsche Forschungsgemeinschaft for his Research Fellowship at the University of Cambridge. David J Wallis acknowledges the support of the EPSRCfellowship (EP/N01202X/2). The authors are grateful to Dr Menno J Kappers and Dr Gunnar Kusch for their critical suggestions. Saptarsi Ghosh thanks Kalyan Kasarla and Terry DevlinfromVeeco™fortheirsupportwiththeMOCVD reactor. 2024-08-15T12:11:30.2536702 2024-06-23T19:55:17.5763331 Faculty of Science and Engineering School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Electronic and Electrical Engineering Saptarsi Ghosh 0000-0003-1685-6228 1 Alexander M Hinz 0000-0002-8845-0086 2 Martin Frentrup 3 Saiful Alam 4 David J Wallis 5 Rachel A Oliver 0000-0003-0029-3993 6 66871__31125__12596a84504546ce8bd6ed0167765f3d.pdf 66871.VoR.pdf 2024-08-15T12:09:54.5704407 Output 21405060 application/pdf Version of Record true Released under the terms of the Creative Commons Attribution 4.0 license. true eng http://creativecommons.org/licenses/by/4.0/
title	Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD
spellingShingle	Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD Saptarsi Ghosh
title_short	Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD
title_full	Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD
title_fullStr	Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD
title_full_unstemmed	Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD
title_sort	Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD
author_id_str_mv	3e247ecabd6eddd319264d066b0ce959
author_id_fullname_str_mv	3e247ecabd6eddd319264d066b0ce959_***_Saptarsi Ghosh
author	Saptarsi Ghosh
author2	Saptarsi Ghosh Alexander M Hinz Martin Frentrup Saiful Alam David J Wallis Rachel A Oliver
format	Journal article
container_title	Semiconductor Science and Technology
container_volume	38
container_issue	4
container_start_page	044001
publishDate	2023
institution	Swansea University
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doi_str_mv	10.1088/1361-6641/acb9b6
publisher	IOP Publishing
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description	For the growth of low-defect crack-free GaN heterostructures on large-area silicon substrates, compositional grading of AlGaN is a widely adapted buffer technique to restrict the propagation of lattice-mismatch induced defects and balance the thermal expansion mismatch-induced tensile stress. So far, a consolidation of the design strategy of such step-graded buffers has been impaired by the incomplete understanding of the effect of individual buffer design parameters on the mechanical and microstructural properties of the epilayers. Herein, we have analyzed a series of metal-organic chemical vapor deposition grown GaN/graded-AlGaN/AlN/Si heterostructures through in situ curvature measurements and post-growth x-ray diffraction (XRD). Our results reveal that in such epi structures, the GaN layer itself induces more compressive stress than the AlGaN buffer, but the underlying AlGaN layers dictate the magnitude of this stress. Furthermore, for a fixed AlGaN buffer thickness, the mean-stress accumulated during the GaN growth is found to be correlated with its structural properties. Specifically, one µm thick GaN layers that acquire 1.50 GPa or higher compressive mean-stress are seen to possess XRD ω-FWHM values less than 650 arc-sec. Also, the evolution of instantaneous stresses during the growth of the AlGaN layers is found to be a valuable indicator for buffer optimization, and composition difference between successive layers is established as a crucial criterion. The results also show that increasing the total buffer thickness (for a fixed number of steps) or increasing the number of steps (for a fixed total buffer thickness) may not always be beneficial. Irrespective of the buffer thickness, optimized high electron mobility transistor structures show similarly low sheet-resistance (∼350 Ω □)−1 and high mobility (∼2000 cm2 V−1 s −1) at room temperature.
published_date	2023-04-01T12:11:29Z
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Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD

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