José M. Iglesias

Hot carrier and hot phonon coupling during ultrafast relaxation of photoexcited electrons in graphene

We study, by means of a Monte Carlo simulator, the hot phonon effect on the relaxation dynamics in photoexcited graphene and its quantitative impact as compared to considering an equilibrium phonon distribution. Our multi-particle approach indicates that neglecting the hot phonon effect significantly underestimates the relaxation times in photoexcited graphene. The hot phonon effect is more important for a higher energy of the excitation pulse and photocarrier densities between

Noise temperature in graphene at high frequencies

1

Carrier-carrier and carrier-phonon interactions in the dynamics of photoexcited electrons in graphene

and

Spectral density of velocity fluctuations under switching field conditions in graphene

3\times 10^{12} \mathrm{~cm}^{-2}

Influence of systematic gate alignment variations on static characteristics in DG-SB-MOSFETs

. Acoustic intervalley phonons play a non-negligible role, and emitted phonons with wavelengths limited up by a maximum (determined by the carrier concentration) induce a slower carrier cooling rate. Intrinsic phonon heating is damped in graphene on a substrate due to additional cooling pathways, with the hot phonon effect showing a strong inverse dependence with the carrier density.

Monte Carlo modeling of mobility and microscopic charge transport in supported graphene

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 on-substrate cases tend to be minimized. The values obtained are comparable to those observed in GaAs and semiconductor nitrides.

Effect of charged impurity scattering on the electron diffusivity and mobility in graphene

In this work we use the Monte Carlo method to simulate the photoexcited carrier relaxation dynamics in suspended monolayer graphene to unveil the role of the different scattering mechanisms involved. The results show a strong activity of carrier-carrier and carrier-optical phonon interactions in the very early stages of the relaxation process driving the thermalization and cooling dynamics. The consideration of the coupling between the electron and phonon population reveals an intense damping in the cooling rates that is dependent on the pumped carrier concentration.

A combined Monte Carlo-balance equations investigation of the high frequency response of graphene

In this paper we present an analysis of the velocity fluctuations during transient regimes arising from an abrupt shift of the electric field in bulk monolayer graphene. For this purpose a material Ensemble Monte Carlo simulator is used to examine these fluctuations by means of the transient autocorrelation function and power spectral density. The evolution of these quantities as well as the non-stationary phenomena taking place during the transients is explained with a microscopic approach.

Impact of self-heating and hot phonons on the drift velocity in graphene

The main objective of this paper is to study the effects of variability in the position of the gates in Double-Gate Schottky-barrier MOSFETs by means of the Monte Carlo method. Taking a device with double gate and perfectly aligned contacts as a starting point, simulations were systematically performed to assess the impact of different types of gate misalignment that may appear. A complete picture of the problem is provided in relation to static device parameters, determining the influence of these factors on performance variability. Results manifest that SB-MOSFETs are extremely sensitive to gate misalignment, as, in extreme cases, drain current can reach relative variations up to 120%. This comes as a result of the carrier injection alterations when the gate potential positioning leads to fluctuations in the tunnel barrier which is at the source contact.

High order harmonic generation in graphene

In this work, the influence of the underlying substrate on the mobility and electronic transport in graphene is evaluated by means of an ensemble Monte Carlo simulator. The substrates considered are h-BN, SiC, SiO2 and HfO2. The substrate type strongly affects the low-field mobility, particularly at room temperature; however, at low temperature the differences between supported graphene and suspended graphene tend to reduce due to a minor influence of surface polar phonon interactions. At room temperature, the anisotropy and inelasticity of SPP interactions yield lower average energies and larger drift velocities at high electric fields for all substrates. The overall results show the excellent performance (from the electronic transport point of view) of graphene on h-BN and SiC substrates at low and high temperatures.