1/ f Noise in Graphene Field-Effect Transistors: Dependence on the Device Channel Area
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1/f Noise in Graphene Field-Effect Transistors: Dependence on the Device Channel Area Guanxiong Liu1, Sergey Rumyantsev2,3, William Stillman2, Michael Shur2 and Alexander A. Balandin1 1 2 3
Department of Electrical Engineering, University of California, Riverside, California 92521 Rensselaer Polytechnic Institute, Troy, New York 12180 Ioffe Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia
ABSTRACT We carried out a systematic experimental study of the low-frequency noise characteristics in a large number of single and bilayer graphene transistors. The prime purpose was to determine the dominant noise sources in these devices and the effect of aging on the current-voltage and noise characteristics. The analysis of the noise spectral density dependence on the surface area of the graphene channel indicates that the dominant contributions to the 1/f electronic noise come from the graphene channel region itself. Aging of graphene transistors due to exposure to ambient for over a month resulted in substantially increased noise, which was attributed to the decreasing mobility of graphene and increasing contact resistance. The noise spectral density in both single and bilayer graphene transistors shows a non-monotonic dependence on the gate bias. This observation confirms that the 1/f noise characteristics of graphene transistors are qualitatively different from those of conventional silicon metal-oxide-semiconductor field-effect transistors. INTRODUCTION The extremely high mobility and saturation velocity make graphene a promising material for the high-frequency and communication applications. A triple-mode graphene amplifier, which capitalizes on the ambipolar nature of graphene has already been demonstrated [1]. Most of the proposed communication applications of graphene require a low-level of the low-frequency noise. The low-frequency noise can be up-converted due to device non-linearity, and contributes to the phase noise of the systems. We have previously reported measurements of the noise in the bottom-gate [2] and top-gate graphene transistors [3]. At the same time, a number of issues such as the effects of surface, contacts, environmental exposure, and temperature on the noise level are still remain open. The exact mechanism of 1/f noise in graphene is also not known. Here we describe the results of the measurements in a large number of graphene devices over an extended time period, which allowed us to elucidate the effects of environmental exposure. For all examined devices the noise spectra for the frequency range 1 Hz-50 kHz were close to the 1/fȖ with Ȗ=1.0-1.1 [4]. Aging of graphene transistors for over a month resulted in substantially increased noise attributed to the decreasing mobility of graphene and increasing contact resistance. The noise spectral density in both single layer graphene (SLG) and bilayer graphene (BLG) transistors either increased with deviation from the charge neutrality point or depended weakly on the gate bias. This observation confirms that the low-frequency nois
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