Article

# Reduction of the self-forces in Monte Carlo simulations of semiconductor devices on unstructured meshes.

Computer Physics Communications (Impact Factor: 2.41). 01/2010; 181:24-34. DOI: 10.1016/j.cpc.2009.08.013

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**ABSTRACT:**Multi-scale modelling of the electron transport via a metal–semiconductor interface is carried out by coupling ab initio calculations with three-dimensional finite element ensemble Monte Carlo simulations. The results for the studied Mo/GaAs structure show that the metal's effect on the electronic properties of the semiconductor varies with the distance from the interface. Introducing this variation into Monte Carlo simulations strongly impacts the resultant transport characteristics of the system. We find that, in the case of an atomically abrupt interface, the variation in the electronic properties is on a large enough scale that treating the interface as abrupt in transport simulations is invalid. In particular, the band gap narrowing near the interface lowers the interface resistivity by more than one order of magnitude with respect to that calculated for the idealized Schottky contact: from 2.1×10−8 to 4.7×10−10 Ω cm2. The dependence of the electron effective mass from the distance to the interface also plays an important role bringing the resistivity to 7.9×10−10 Ω cm2.Semiconductor Science and Technology 04/2014; 29(5):054003. · 2.21 Impact Factor -
##### Article: Monte Carlo simulations of mobility in doped GaAs using self-consistent Fermi–Dirac statistics

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**ABSTRACT:**Electron mobility as a function of ionized impurity concentration is calculated in bulk GaAs using ensemble Monte Carlo simulations. The simulations include Fermi–Dirac statistics with self-consistently calculated Fermi energy, and electron temperature which are then used in static and in random phase approximation (q-dependent) screening model and for the Pauli exclusion principle employed after each scattering event. However, when the degeneracy due to the Pauli exclusion principle is considered in the simulations, then electron mobility starts to increase at high doping concentrations demonstrating a breakdown of the model. This breakdown can be prevented by taking into account a change in the semiconductor bandstructure via dopants acting in its lattice. The bandstructure change has been incorporated by increasing electron effective mass which allows us to obtain very good agreement of simulated electron mobility with experimental data.Semiconductor Science and Technology 03/2011; 26(5):055007. · 2.21 Impact Factor -
##### Article: Monte Carlo Study of Ultimate Channel Scaling in Si and In$_{\rm 0.3}$Ga$_{\rm 0.7}$As Bulk MOSFETs

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**ABSTRACT:**A detailed analysis of nonequilibrium electron trans- port in n-type Si and In0 .3 Ga0 .7 As MOSFETs scaled into ultimate limit of 5-nm gate length is carried out using ensemble Monte Carlo device simulations. The analysis is based on simulations of ID - VG characteristics for a template, 25-nm gate length Si MOSFET compared against previous results from various Monte Carlo de- vice codes, and for an equivalent 25-nm gate length In0 .3 Ga0 .7 As MOSFET. The transistors are then laterally scaled from a gate length of 25 nm to 20, 15, 10 and 5 nm monitoring the average electron velocity, energy, and sheet density along the channel at a supply voltage of 1.0 V. A degradation of the injection velocity with the scaling of a gate/channel length is observed. While we have found a decrease in the overall electron velocity profile along the Si channel for gate lengths smaller than 10 nm and a decrease in the injection velocity from a gate length of 20 nm, the increase in the intrinsic drain current in the scaling process is continuous thanks to the increasing velocity at the drain side. However, the velocity in the InGaAs channel MOSFETs increases steadily dur- ing the scaling but the increase in the intrinsic drain current is less pronounced. This is the result of a source starvation, due to a low density of states in III-V semiconductors, which cannot provide a large enough electron sheet density in the channel. This effect is partially mitigated by the enhancement of density of states as a proportion of electrons in the source/drain transfers to upper valleys with a larger electron effective mass.IEEE Transactions on Nanotechnology 01/2011; 10(6):1424-1432. · 1.62 Impact Factor

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