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

Monia Spera, Giuseppe Greco, Raffaella Lo Nigro, Silvia Scalese, Corrado Bongiorno, Marco Cannas, Filippo Giannazzo and Fabrizio Roccaforte
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Monia Spera: Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
Giuseppe Greco: Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
Raffaella Lo Nigro: Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
Silvia Scalese: Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
Corrado Bongiorno: Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
Marco Cannas: Department of Physics and Chemistry, University of Palermo, Via Archirafi, 36, 90123 Palermo, Italy
Filippo Giannazzo: Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
Fabrizio Roccaforte: Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy

Energies, 2019, vol. 12, issue 14, 1-12

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 Al 3 Ti and Al 3 Ta 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 ?cm 2 ) with respect to the Ta/Al/Ta samples (ρ c = 4.0 × 10 −4 ?cm 2 ). 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.

Keywords: AlGaN/GaN; ohmic contacts; barrier height; Ti/Al/Ti; Ta/Al/Ta (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
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