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Open AccessArticle

Metal/Semiconductor Barrier Properties of Non-Recessed Ti/Al/Ti and Ta/Al/Ta Ohmic Contacts on AlGaN/GaN Heterostructures

Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
Department of Physics and Astronomy, University of Catania, Via Santa Sofia, 64, 95123 Catania, Italy
Department of Physics and Chemistry, University of Palermo, Via Archirafi, 36, 90123 Palermo, Italy
Authors to whom correspondence should be addressed.
Energies 2019, 12(14), 2655;
Received: 16 May 2019 / Revised: 21 June 2019 / Accepted: 3 July 2019 / Published: 10 July 2019
(This article belongs to the Special Issue Volume II: Semiconductor Power Devices)
This paper compares the metal/semiconductor barrier height properties of non-recessed Ti/Al/Ti and Ta/Al/Ta contacts on AlGaN/GaN heterostructures. Both contacts exhibited a rectifying behavior after deposition and after annealing at temperatures up to 550 °C. The ohmic behavior was reached after annealing at 600 °C. High-resolution morphological and electrical mapping by conductive atomic force microscopy showed a flat surface for both contacts, with the presence of isolated hillocks, which had no significant impact on the contact resistance. Structural analyses indicated the formation of the Al3Ti and Al3Ta phases upon annealing. Furthermore, a thin interfacial TiN layer was observed in the Ti/Al/Ti samples, which is likely responsible for a lower barrier and a better specific contact resistance (ρc = 1.6 × 10−4 Ωcm2) with respect to the Ta/Al/Ta samples (ρc = 4.0 × 10−4 Ωcm2). The temperature dependence of the specific contact resistance was described by a thermionic field emission mechanism, determining barrier height values in the range of 0.58–0.63 eV. These results were discussed in terms of the different microstructures of the interfaces in the two systems. View Full-Text
Keywords: AlGaN/GaN; ohmic contacts; barrier height; Ti/Al/Ti; Ta/Al/Ta AlGaN/GaN; ohmic contacts; barrier height; Ti/Al/Ti; Ta/Al/Ta
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Spera, M.; Greco, G.; Lo Nigro, R.; Scalese, S.; Bongiorno, C.; Cannas, M.; Giannazzo, F.; Roccaforte, F. Metal/Semiconductor Barrier Properties of Non-Recessed Ti/Al/Ti and Ta/Al/Ta Ohmic Contacts on AlGaN/GaN Heterostructures. Energies 2019, 12, 2655.

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