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Proceedings Paper

Low-temperature growth of Al-doped ZnO by atomic layer deposition for plasmonics (Conference Presentation)
Author(s): Dhruv Fomra; Kai Ding; Vitaliy S. Avrutin; Natalia Izyumskaya; Nathaniel Kinsey; Ümit Özgür; Hadis Morkoç

Paper Abstract

Transparent conducting oxides, such as Ga-doped ZnO (GZO) and Al-doped ZnO (AZO) are attractive materials for high-performance plasmonic devices operating at telecommunication wavelengths. In this contribution, we compare the growth of epsilon-near-zero GZO and AZO films on sapphire by two different deposition techniques: molecular beam epitaxy (MBE) and atomic layer deposition (ALD). For MBE of GZO, a multiple buffer consisted of a high-temperature MgO layer, a low-temperature ZnO, followed by a high-temperature ZnO layer is employed to assure the crystalline quality of the GZO film. By controlling the growth parameters, including Ga doping level, VI/II ratio, substrate temperature, we are able to produce GZO films at 350 °C with electron mobility between 30 and 50 cm2/V.s, electron concentration up to 7×1020 cm-3, and resistivity down to 2.5×10-4 Ω.cm. For ALD of AZO, without using any buffer, by reducing the Al pulse duration, we are able to grow the AZO films under a large ratio of Al to Zn pulses of 1:6, which improves the activation of Al as an effective dopant. Hence AZO films with electron concentration above 7×1020 cm-3, electron mobility between 10 and 20 cm2/V.s, and resistivity below 6×10-4 Ω.cm have been obtained at 250 °C. The corresponding epsilon-near-zero point in the ALD-grown material was tuned down to 1470 nm. Our data indicate that the ALD method provides a low-temperature route to plasmonic TCOs for telecommunication wavelength range. Effect of electron mobility on optical loss and, therefore, plasmonic figure of merit is discussed.

Paper Details

Date Published: 10 March 2020
Proc. SPIE 11281, Oxide-based Materials and Devices XI, 1128119 (10 March 2020); doi: 10.1117/12.2550537
Show Author Affiliations
Dhruv Fomra, Virginia Commonwealth Univ. (United States)
Kai Ding, Virginia Commonwealth Univ. (United States)
Vitaliy S. Avrutin, Virginia Commonwealth Univ. (United States)
Natalia Izyumskaya, Virginia Commonwealth Univ. (United States)
Nathaniel Kinsey, Virginia Commonwealth Univ. (United States)
Ümit Özgür, Virginia Commonwealth Univ. (United States)
Hadis Morkoç, Virginia Commonwealth Univ. (United States)

Published in SPIE Proceedings Vol. 11281:
Oxide-based Materials and Devices XI
David J. Rogers; David C. Look; Ferechteh H. Teherani, Editor(s)

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