Noise temperature in graphene at high frequencies

Abstract

A numerical method for obtaining the frequency-dependent noise temperature in monolayer graphene is presented. From the mobility and diffusion coefficient values provided by Monte Carlo simulation, the noise temperature in graphene is studied up to the THz range, considering also the influence of different substrate types. The influence of the applied electric field is investigated: the noise temperature is found to increase with the applied field, dropping down at high frequencies (in the sub-THz range). The results show that the low-frequency value of the noise temperature in graphene on a substrate tends to be reduced as compared to the case of suspended graphene due to the important effect of remote polar phonon interactions, thus indicating a reduced emitted noise power; however, at very high frequencies the influence of the substrate tends to be significantly reduced, and the differences between the suspended and onsubstrate cases tend to be minimized. The values obtained are comparable to those observed in GaAs and semiconductor nitrides.

Harmonic Extraction in Graphene: Monte Carlo Analysis of the Substrate Influence

“…The efficiency of graphene for high-order harmonic generation has already been revealed [ 4 ], and tunable resonances characterised by large Q-factors have been observed in the THz regime [ 13 ]; on the other hand, we have previously evidenced the potentiality of free-standing graphene, concluding that it is possible to reach the THz range in alike conditions than III–V materials [ 5 ]; however, attending to the actual requirements of the experimental works, it is important to develop these analyses for monolayer graphene on different substrates. Ensemble Monte Carlo (MC) simulations [ 12 ] have been used for this aim, such modelling tools being highly convenient for determining and studying parameters such as velocity correlation function or noise temperature [ 14 ]. The great advantage of the MC procedure is that the sources of fluctuations are intrinsically assimilated through the stochastic nature of the different scattering events.…”