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The Endocyclic Carbon Substituent of Guanidinate and Amidinate Precursors Controlling ALD of InN Films

preprint
submitted on 19.06.2019 and posted on 19.06.2019 by Polla Rouf, Nathan J O'Brien, Karl Rönnby, Rouzbeh Samii, Ivan G. Ivanov, Lars Ojamäe, Henrik Pedersen

Indium nitride (InN) is an interesting material for future high frequency electronics, due to its high electron mobility. The problematic deposition of InN films currently prevents full exploration of InN based electronics. We present studies of atomic layer deposition (ALD) of InN using In precursors with bidentate ligands forming In–N bonds; tris(N,N-dimethyl-N’,N’’-diisoproprylguanidinato)indium(III), tris(N,N’-diisopropylamidinato)indium(III) and tris(N,N’-diisopropylformamidinato)indium(III). These compounds form a series were the size of the substituent in the endocyclic position decreases from –NMe2, to –Me and to –H, respectively. We show that when the size of the substituent decreases, InN films with higher crystalline- and optical quality, lower roughness and an In/N ratio closer to unity is achieved. From quantum chemical calculations we show that the smaller substituents lead to less steric repulsion and weaker bonds between the ligand and In centre. We propose that these effects render a more favoured surface chemistry for the nitidisation step in the ALD cycle which explains the improved film properties.

Funding

This project was founded by the Swedish foundation for Strategic Research through the project “Time-resolved low temperature CVD for III-nitrides” (SSF-RMA 15-0018) and by the Knut and Alice Wallenberg foundation through the project “Bridging the THz gap” (No. KAW 2013.0049). L.O. acknowledges financial support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO Mat LiU no. 2009 00971). Supercomputing resources were provided by the Swedish National Infrastructure for Computing (SNIC) and the Swedish National Supercomputer Centre (NSC).

History

Email Address of Submitting Author

henrik.pedersen@liu.se

Institution

Linköping University

Country

Sweden

ORCID For Submitting Author

0000-0002-7171-5383

Declaration of Conflict of Interest

None

Version Notes

Original submission

Exports