Shot and Johnson Noise Measurement in Graphene Using Wide-Bandwidth Measurement Technique*

We measure shot and Johnson noise in single and bilayer graphene devices as a function of carrier density. For this measurement, we have developed a technique for measuring high-frequency wide-bandwidth noise. We use a low-noise RF amplifier, high-frequency digitizer, and digital signal processing to measure noise in the range of several hundred MHz of a device whose resistance can vary several orders of magnitude. We precisely characterize the resistance-dependent gain and noise temperature of the entire circuit using Johnson noise from the device itself, in a temperature range of 3-300K. This technique presents a very flexible measurement of noise from devices, allowing device resistance fluctuations of several orders of magnitude, extreme nonlinear resistance behavior, and highly non-equilibrium conditions.