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Comparative analysis of the effects of tantalum doping and annealing on atomic layer deposited (Ta2O5)(x)(Al2O3)(1-x) as potential gate dielectrics for GaN/AlxGa1-xN/GaN high electron mobility transistors

Partida-Manzanera, T, Roberts, JW, Bhat, TN, Zhang, Z, Tan, HR, Dolmanan, SB, Sedghi, N, Tripathy, S and Potter, RJ (2016) Comparative analysis of the effects of tantalum doping and annealing on atomic layer deposited (Ta2O5)(x)(Al2O3)(1-x) as potential gate dielectrics for GaN/AlxGa1-xN/GaN high electron mobility transistors. Journal of Applied Physics, 119 (2). ISSN 0021-8979

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Abstract

This paper describes a method to optimally combine wide band gap Al2O3 with high dielectric constant (high-κ) Ta2O5 for gate dielectric applications. (Ta2O5)x(Al2O3)1−x thin films deposited by thermal atomic layer deposition (ALD) on GaN-capped AlxGa1−xN/GaN high electron mobility transistor (HEMT) structures have been studied as a function of the Ta2O5 molar fraction. X-ray photoelectron spectroscopy shows that the bandgap of the oxide films linearly decreases from 6.5 eV for pure Al2O3 to 4.6 eV for pure Ta2O5. The dielectric constant calculated from capacitance-voltage measurements also increases linearly from 7.8 for Al2O3 up to 25.6 for Ta2O5. The effect of post-deposition annealing in N2 at 600 °C on the interfacial properties of undoped Al2O3 and Ta-doped (Ta2O5)0.12(Al2O3)0.88 films grown on GaN-HEMTs has been investigated. These conditions are analogous to the conditions used for source/drain contact formation in gate-first HEMT technology. A reduction of the Ga-O to Ga-N bond ratios at the oxide/HEMT interfaces is observed after annealing, which is attributed to a reduction of interstitial oxygen-related defects. As a result, the conduction band offsets (CBOs) of the Al2O3/GaN-HEMT and (Ta2O5)0.16(Al2O3)0.84/GaN-HEMT samples increased by ∼1.1 eV to 2.8 eV and 2.6 eV, respectively, which is advantageous for n-type HEMTs. The results demonstrate that ALD of Ta-doped Al2O3 can be used to control the properties of the gate dielectric, allowing the κ-value to be increased, while still maintaining a sufficient CBO to the GaN-HEMT structure for low leakage currents. VC 2016 AIP Publishing LLC

Item Type: Article
Additional Information: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Journal of Applied Physics and may be found at http://dx.doi.org/10.1063/1.4939298
Uncontrolled Keywords: 01 Mathematical Sciences, 02 Physical Sciences, 09 Engineering
Subjects: T Technology > TK Electrical engineering. Electronics. Nuclear engineering
Divisions: General Engineering Research Institute
Publisher: AIP Publishing
Related URLs:
Date Deposited: 03 Aug 2018 11:37
Last Modified: 18 Sep 2018 10:47
DOI or Identification number: 10.1063/1.4939298
URI: http://researchonline.ljmu.ac.uk/id/eprint/9052

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