Contributors: Centre de Nanosciences et de Nanotechnologies (C2N); Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS); Centrale de Micro Nano Fabrication - IEMN (CMNF - IEMN); Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520 (IEMN); Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF)-JUNIA (JUNIA); Université catholique de Lille (UCL)-Université catholique de Lille (UCL)-Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF)-JUNIA (JUNIA); Université catholique de Lille (UCL)-Université catholique de Lille (UCL); Georgia Institute of Technology Lorraine, France; Georgia Tech Lorraine Metz; Georgia Institute of Technology Atlanta -Ecole Supérieure d'Electricité - SUPELEC (FRANCE)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC); Université Bourgogne Franche-Comté COMUE (UBFC)-Université Bourgogne Franche-Comté COMUE (UBFC)-Arts et Métiers Sciences et Technologies; Georgia Institute of Technology Atlanta; The authors thank Francesco Daddi of Grenoble INP Phelma, France for taking part in TLM characterizations and Hannah Lias of South Dakota School of Mines and Technology, USA for proofreading the manuscript during their internship in the C2N laboratory. Part of this work was supported by ANR project CORTIORGAN (No. ANR-22-CE08-0020-03), and ANR project NEWAVE (No. ANR-21-CE24-0019-04). C2N and IEMN are members of RENATECH, the national network of large academic micro-nanofabrication facilities. FIB equipment co-funding: CPER Hauts de France project IMITECH and the Métropole Européenne de Lille.; CMNF; CPER IMITECH; ANR-22-CE08-0020,CORTIORGAN,Stimulateur optique d'implant de faible taille et haute densité à base de LEDs minces détachable(2022); ANR-21-CE24-0019,NEWAVE,Nouveaux concepts pour micro- et nano-lasers à guide d'onde(2021)
نبذة مختصرة : International audience ; High-resolution transmission electron microscopy (TEM) coupled to energy dispersive X-ray spectroscopy (EDX) is used to clarify the exact role of Ni-Au-Ga interdiffusion mechanisms taking place during rapid thermal annealing under an oxygen atmosphere of a Ni-Au/p-GaN contact. It is shown that oxygen-assisted, Ni diffusion to the top surface of the metallic contact through the formation of a nickel oxide (NiO x ) is accompanied by Au diffusion down to the GaN surface and by Ga out-diffusion through the GaN/metal interface. Electrical characterizations of the contact by a transmission line method show that an ohmic contact is obtained as soon as a thin, Au-Ga interfacial layer is formed, even after complete diffusion of Ni or NiO x to the top surface of the contact. Our results clarify that the presence of Ni or NiO x at the interface is not the main origin of the ohmic-like behavior in such contacts. Auto-cleaning of the interface during the interdiffusion process may play a role, but TEM-EDX analysis evidences that the creation of Ga vacancies associated with the formation of a Ga-Au interfacial layer is crucial for reducing the Schottky barrier height and maximizing the amount of current flowing through the contact.
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