Contact properties to CVD-graphene on GaAs substrates for optoelectronic applications

• Published in: Nanotechnology 2014-08, Vol.25 (33), p.335707-335707
• Main Authors: Babichev, A V, Gasumyants, V E, Egorov, A Yu, Vitusevich, S, Tchernycheva, M
• Format: Article
• Language: English
• Subjects: Contact; contact properties; Contact resistance; CVD-graphene; GaAs substrates; Gallium arsenide; Gallium arsenides; Graphene; Monolayers; optoelectronic devices; Silicon dioxide; Silicon substrates
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/25/33/335707

The optimization of contacts between graphene and metals is important for many optoelectronic applications. In this work, we evaluate the contact resistance and sheet resistance of monolayer and few-layered graphene with different metallizations using the transfer length method (TLM). Graphene was obtained by the chemical vapor deposition technique (CVD-graphene) and transferred onto GaAs and Si/SiO2 substrates. To account for the quality of large-area contacts used in a number of practical applications, a millimeter-wide TLM pattern was used for transport measurements. Different metals-namely, Ag, Pt, Cr, Au, Ni, and Ti-have been tested. The minimal contact resistance Rc obtained in this work is 11.3 kΩ μm for monolayer CVD-graphene, and 6.3 kΩ μm for a few-layered graphene. Annealing allows us to decrease the contact resistance Rc and achieve 1.7 kΩm μm for few-layered graphene on GaAs substrate with Au contacts. The minimal sheet resistance Rsh of few-layered graphene transferred to GaAs and Si/SiO2 substrates are 0.28 kΩ/□ and 0.27 kΩ/□. The Rsh value of monolayer graphene on the GaAs substrate is 8 times higher (2.3 kΩ/□), but it reduces for the monolayer graphene on Si/SiO2 (1.4 kΩ/□). For distances between the contacts below 5 μm, a considerable reduction in the resistance per unit length was observed, which is explained by the changes in doping level caused by graphene suspension at small distances between contact pads.