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; https://doi.org/10.3390/en12142655

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)

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Abstract

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 (ρ_c = 1.6 × 10⁻⁴ Ωcm²) with respect to the Ta/Al/Ta samples (ρ_c = 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

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MDPI and ACS Style

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. https://doi.org/10.3390/en12142655

AMA Style

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(14):2655. https://doi.org/10.3390/en12142655

Chicago/Turabian Style

Spera, Monia, Giuseppe Greco, Raffaella Lo Nigro, Silvia Scalese, Corrado Bongiorno, Marco Cannas, Filippo Giannazzo, and Fabrizio Roccaforte. 2019. "Metal/Semiconductor Barrier Properties of Non-Recessed Ti/Al/Ti and Ta/Al/Ta Ohmic Contacts on AlGaN/GaN Heterostructures" Energies 12, no. 14: 2655. https://doi.org/10.3390/en12142655

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

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