Elucidating the role of nitrogen plasma composition in the low-temperature self-limiting growth of indium nitride thin films

Saidjafarzoda Ilhom; Adnan Mohammad; Deepa Shukla; John Grasso; Brian G. Willis; Ali K. Okyay; Necmi Biyikli

doi:10.1039/D0RA04567E

Elucidating the role of nitrogen plasma composition in the low-temperature self-limiting growth of indium nitride thin films†

Saidjafarzoda Ilhom,

^a Adnan Mohammad,^a Deepa Shukla,^ab John Grasso,^c Brian G. Willis,^c Ali K. Okyay

^d and Necmi Biyikli

*^ab

Author affiliations

* Corresponding authors

^a Department of Electrical & Computer Engineering, University of Connecticut, 371 Fairfield Way, Storrs, CT 06269, USA
E-mail: necmi.biyikli@uconn.edu
Tel: +1-860-486-2666

^b Department of Materials Science & Engineering, University of Connecticut, 97 North Eagleville Road, Storrs, CT 06269, USA

^c Department of Chemical and Biomolecular Engineering, University of Connecticut, 191 Auditorium Road, Storrs, CT 06269, USA

^d Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA

Abstract

In this work, we have studied the role varying nitrogen plasma compositions play in the low-temperature plasma-assisted growth of indium nitride (InN) thin films. Films were deposited on Si (100) substrates using a plasma-enhanced atomic layer deposition (PE-ALD) reactor featuring a capacitively-coupled hollow-cathode plasma source. Trimethylindium (TMI) and variants of nitrogen plasma (N₂-only, Ar/N₂, and Ar/N₂/H₂) were used as the metal precursor and nitrogen co-reactant, respectively. In situ ellipsometry was employed to observe individual ligand exchange and plasma-assisted ligand removal events in real-time during the growth process. Only the samples grown under hydrogen-free nitrogen plasmas (Ar/N₂ or N₂-only) resulted in nearly stoichiometric single-phase crystalline hexagonal InN (h-InN) films at substrate temperatures higher than 200 °C under 100 W rf-plasma power. Varying the plasma gas composition by adding H₂ led to rather drastic microstructural changes resulting in a cubic phase oxide (c-In₂O₃) film. Combining the in situ measured growth evolution with ex situ materials characterization, we propose a simplified model describing the possible surface reactions/groups during a unit PE-ALD cycle, which depicts the highly efficient oxygen incorporation in the presence of hydrogen radicals. Further structural, chemical, and optical characterization have been carried out on the optimal InN films grown with Ar/N₂ plasma to extract film properties. Samples grown at lower substrate temperature (160 °C) and reduced/elevated rf-plasma power levels (50/150 W) displayed similar amorphous character, which is attributed to either insufficient surface energy or plasma-induced crystal damage. InN samples grown at 240 °C under 100 W rf-plasma showed clear polycrystalline h-InN layers with ∼20 nm average-sized single crystal domains exhibiting hexagonal symmetry.

RSC Advances

Elucidating the role of nitrogen plasma composition in the low-temperature self-limiting growth of indium nitride thin films†

Abstract

Supplementary files

Article information

Download Citation

Permissions

Elucidating the role of nitrogen plasma composition in the low-temperature self-limiting growth of indium nitride thin films

Social activity

Search articles by author

Spotlight

Advertisements