Direct evidence of an Al alloyed SiNx interlayer within an ammonia predosed AlN/Si interface via STEM-EELS

Simon Fairclough^a, Alexander Hinz^a, Saptarsi Ghosh^a, Bogdan Spiridon^a, David Wallis^a^,^b, Rachel Oliver^a

^aDepartment of Material Science and Metallurgy, University of Cambridge, Charles Babbage Road, 27, United Kingdom

^bCentre for High Frequency Engineering, University of Cardiff, Cardiff CF24 3AA, United Kingdom

Proceedings of Electron Beam Spectroscopy for Nanooptics 2021 (EBSN2021)

Online, Spain, 2021 June 14th - 15th

Organizers: Mathieu Kociak and Nahid Talebi

Poster, Simon Fairclough, 020
Publication date: 8th June 2021

ePoster:

Gallium nitride (GaN) and its alloys with Aluminium (Al) and Indium have shown great application within the electronic and optoelectronic fields due to their wide and tuneable band gap, high defect tolerance within devices, high breakdown voltage and high saturation velocity[1]. A cost effective route towards these devices has been to grow GaN on Silicon (Si) substrates via metalorganic vapour phase epitaxy (MOVPE)[2]. These structures show good performance compared to GaN devices on other substrates such as sapphire or silicon carbide, but do require an aluminium nitride nucleation layer and a significant amount of subsequent strain management within the buffer layers to enable a low wafer bow and to prevent wafer cracking[2].

Previous studies have shown that predosing the Si wafer surface with either trimethylaluminium (TMA) or ammonia before AlN growth can have an appreciable impact on wafer bow[3]. Many questions still remain as to the importance and role of the predose in the growth of the AlN and subsequent strain management. Previous electron microscopy studies have inferred the formation of both amorphous and crystalline silicon nitride (SiNx) interlayers, but with little compositional analysis due to the relatively large spatial resolution of electron dispersive x-ray spectroscopy (EDS)[3]. Other studies have used STEM-electron energy loss spectroscopy (EELS) which offers sub nm spatial resolution of the interface, and has been used to great effect for compositional analysis within TMA predose studies[4,5].

In this study we investigate a series of samples with different durations of ammonia predose via STEM-EELS, to not only probe the composition of the interface, but also to obtain chemical bonding information within this layer. Here we are able to show direct evidence of a SiN_x interlayer up to 5.3 nm thick with an ammonia predose time dependency, and for the first time highlight an Al alloying of the SiN_x[6].

References:

[1] Amano, H.; Baines, Y.; Beam, E.; Borga, M.; Bouchet, T.; Chalker, P. R.; Charles, M.; Chen, K. J.; Chowdhury, N.; Chu, R.; De Santi, C.; De Souza, M. M.; Decoutere, S.; Di Cioccio, L.; Eckardt, B.; Egawa, T.; Fay, P.; Freedsman, J. J.; Guido, L.; Häberlen, O.; Haynes, G.; Heckel, T.; Hemakumara, D.; Houston, P.; Hu, J.; Hua, M.; Huang, Q.; Huang, A.; Jiang, S.; Kawai, H.; Kinzer, D.; Kuball, M.; Kumar, A.; Lee, K. B.; Li, X.; Marcon, D.; März, M.; McCarthy, R.; Meneghesso, G.; Meneghini, M.; Morvan, E.; Nakajima, A.; Narayanan, E. M. S.; Oliver, S.; Palacios, T.; Piedra, D.; Plissonnier, M.; Reddy, R.; Sun, M.; Thayne, I.; Torres, A.; Trivellin, N.; Unni, V.; Uren, M. J.; Van Hove, M.; Wallis, D. J.; Wang, J.; Xie, J.; Yagi, S.; Yang, S.; Youtsey, C.; Yu, R.; Zanoni, E.; Zeltner, S.; Zhang, Y. The 2018 GaN Power Electronics Roadmap. Journal of Physics D: Applied Physics. Institute of Physics Publishing March 26, 2018, p 163001.

[2] Zhu, D.; Wallis, D. J.; Humphreys, C. J. Prospects of III-Nitride Optoelectronics Grown on Si. Reports Prog. Phys. 2013, 76 (10), 106501.

[3] Li, Y.; Wang, W.; Li, X.; Huang, L.; Zheng, Y.; Chen, X.; Li, G. Nucleation Layer Design for Growth of a High-Quality AlN Epitaxial Film on a Si(111) Substrate. CrystEngComm 2018, 20 (11), 1483–1490.

[4] Radtke, G.; Couillard, M.; Botton, G. A.; Zhu, D.; Humphreys, C. J. Structure and Chemistry of the Si(111)/AlN Interface. Appl. Phys. Lett. 2012, 100 (1), 011910.

[5] Radtke, G.; Couillard, M.; Botton, G. A.; Zhu, D.; Humphreys, C. J. Scanning Transmission Electron Microscopy Investigation of the Si(111)/AlN Interface Grown by Metalorganic Vapor Phase Epitaxy. Appl. Phys. Lett. 2010, 97 (25), 251901.

[6] Ghosh, S.; Hinz, A.; Fairclough, S.; Spiridon, B.; Eblabla, A.; Casbon, M.; Kappers, M.; Elgaid, K.; Alam, S.; Oliver, R.; Wallis, D. Origin(s) of Anomalous Substrate Conduction in MOVPE-Grown GaN HEMTs on Highly Resistive Silicon. ACS Appl. Electron. Mater. 2021, 3, 2, 813–824

Acknowledgements:

This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) under the grant InGaNET,“Integration of RF Circuits with High Speed GaNS witching on Silicon Substrates”(EP/N017927/1) and (EP/N014820/2) and 'Hetero-print': A holistic approach to transfer-printing for heterogeneous integration in manufacturing (EP/R03480X/1) . A.H. acknowledges the Deutsche Forschungsge-meinschaft for his Research Fellowship at the University of Cambridge. D.J.W. acknowledges the support of EPSRC fellowship (EP/N01202X/2)

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