A Study of the Photoresponse in Graphene Produced by Chemical Vapor Deposition
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ICATION, TREATMENT, AND TESTING OF MATERIALS AND STRUCTURES
A Study of the Photoresponse in Graphene Produced by Chemical Vapor Deposition A. V. Babicheva,*, S. A. Kadinskayaa, K. Yu. Shubinaa, A. A. Vasilieva, A. A. Blokhinb,c, E. I. Moiseevd, S. A. Blokhinc, I. S. Mukhina,e, I. A. Eliseyevc, V. Yu. Davydovc, P. N. Brunkovc, N. V. Kryzhanovskayad, and A. Yu. Egorove a
Saint Petersburg National Research Academic University of the Russian Academy of Sciences, St. Petersburg, 194021 Russia b Submicrometer Heterostructures for Microelectronics Research & Engineering Center, Russian Academy of Sciences, St. Petersburg, 194021 Russia c Ioffe Institute, St. Petersburg, 194021 Russia d National Research University Higher School of Economics, St. Petersburg, 190008 Russia e ITMO University, St. Petersburg, 197101 Russia *e-mail: [email protected] Received May 6, 2020; revised May 12, 2020; accepted May 12, 2020
Abstract—The results of experiments aimed at fabricating and studying the properties of photodetector structures based on single-layer graphene produced by chemical vapor deposition are presented. The configuration of a Ta2O5 vertical microcavity with a resonance wavelength of about 850 nm and a lower dielectric SiO2/Ta2O5 distributed Bragg reflector is taken as the base structure. The conditions for the transfer and fabrication of mesas in the graphene layer on the microcavity surface are optimized. The diagnostics by Raman spectroscopy of the structural quality of graphene after fabrication of the mesas in the graphene layer and contact pads are indicative of the single-layer structure of graphene with a low intensity of features in its spectrum, responsible for imperfection of the structure. The photocurrent is measured under local optical pumping. Keywords: photodetector structures, monolayer graphene, microcavity, mesa DOI: 10.1134/S1063782620090031
1. INTRODUCTION Together with active studies concerned with photodetectors based on AIIIBV compounds [1, 2], strong interest has been observed recently in new types of photodetectors, including those based on graphene [3–23]. At a thickness of 3.35 Å, graphene has an absorption coefficient that exceeds by 1–3 orders of magnitude that of typical semiconductors (InGaAs, GaAs, Ge) [24]. However, due to a small interaction length, graphene absorbs only 2.3% of the incident light (which corresponds to the visible spectral range) [25]. In contrast to the majority of other materials, graphene has no bandgap, and, therefore, there are limitations on the absorption wavelength (no absorption edge). As a consequence, graphene absorbs light from the UV to the terahertz spectral range [12, 26–28]. Several approaches to raising the absorption of graphene have been suggested. The main of these are the following: the use of plasmon nanostructures [29], use of nanoparticles [30], integration of graphene into a waveguide configuration [4, 30–32], the formation of doped graphene disks [33], the formation of graphene–insulator superlattices [34], integration
with photosensiti
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