Formation of Ohmic Contacts to a Diamond-Like Carbon Layer Deposited on a Dielectric Diamond Substrate
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INTERNATIONAL SYMPOSIUM “NANOPHYSICS AND NANOELECTRONICS”, NIZHNY NOVGOROD, MARCH 10–13, 2020
Formation of Ohmic Contacts to a Diamond-Like Carbon Layer Deposited on a Dielectric Diamond Substrate A. I. Okhapkina,*, P. A. Yunina, E. A. Arkhipovaa, S. A. Kraeva, S. A. Korolyova, M. N. Drozdova, and V. I. Shashkina† a Institute
for Physics of Microstructures, Russian Academy of Sciences, Afonino, Kstovskii rayon, Nizhny Novgorod oblast, 603950 Russia *e-mail: [email protected] Received April 15, 2020; revised April 21, 2020; accepted April 21, 2020
Abstract—The fabrication process of ohmic contacts to a diamond-like carbon (DLC) layer is described with the sequential deposition of a Au/Mo/Ti metallic layer onto it. The contacts have good mechanical and adhesion properties. Their specific contact resistance is varied from 1.4 × 10–4 to 6.4 × 10–5 Ω cm2 depending on the DLC layer thickness. The temperature dependence of the layer film resistance is investigated. It is shown that thin DLC layers provide better characteristics of an ohmic contact due to their more uniform graphitization during thermal annealing. Keywords: diamond-like carbon, ohmic contacts, plasma-chemical deposition, single-crystal diamond, thermal annealing DOI: 10.1134/S1063782620090213
1. INTRODUCTION Single-crystal diamond possesses a high thermal conductivity, hardness, and chemical inertness. Currently, it is considered as one of the promising materials for future semiconductor devices [1]. At the same time, many important manufacturing problems have not been solved for semiconductor diamond. In particular, the high activation energy of impurities in diamond complicates the design of devices with current flow because the formation of ohmic contacts with a low contact resistivity ρcont is complicated. The formation method of ohmic contacts to a diamond single crystal with the application of carbide-forming metals is described in [2, 3]. The authors of recent work [3] fabricated non-alloyed Au/Mo/Ti ohmic contacts to p-type epitaxial diamond films with ρcont = 4 × 10–7 Ω cm2 and investigated the influence of annealing on their properties. It turned out that the molybdenum layer during annealing prevents titanium diffusion into gold and oxidation of the Ti/C contact region. The authors of [4] showed that the addition of a thin diamond-like carbon (DLC) sublayer 1–3 nm in thickness improves the properties of Pt/Au ohmic contacts when fabricating diamond radiation detectors. Due to the quantum tunneling effect, electrons from metals easily pass through the thin DLC layer to diamond. † Deceased.
In this work, we present the results of the first developmental stage of ohmic contacts to diamond using a DLC sublayer and Au/Mo/Ti metals. The use of the DLC sublayer noticeably improves the adhesion of combined contacts to diamond, which facilitates the performance of photolithographic operations. In contrast with the known formation methods of graphite contacts to diamond under the effect of a laser or ion irradiation [5, 6], the use of DLC makes i
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