Electron transport properties in high-purity Ge down to cryogenic temperatures

Electron transport in Ge at various temperatures down to 20 mK has been investigated using particle Monte Carlo simulation taking into account ionized impurity and inelastic phonon scattering. The simulations account for the essential features of electron transport at cryogenic temperature: Ohmic regime, anisotropy of the drift velocity relative to the direction of the electric field, as well as a negative differential mobility phenomenon along the field orientation. Experimental data for the electron velocities are reproduced with a satisfactory accuracy. Examples of electron position in the real space during the simulations are given and evidence separated clouds of electrons propagating along different directions depending on the valley they belong.Comment: 24 pages, 11 figure

Drain current computation in nanoscale nMOSFETs: Comparison of transport models

n/

Electron effective mobility in strained Si/Si1-xGex MOS devices using Monte Carlo simulation

Based on Monte Carlo simulation, we report the study of the inversion layer mobility in n-channel strained Si/ Si1-xGex MOS structures. The influence of the strain in the Si layer and of the doping level is studied. Universal mobility curves mueff as a function of the effective vertical field Eeff are obtained for various state of strain, as well as a fall-off of the mobility in weak inversion regime, which reproduces correctly the experimental trends. We also observe a mobility enhancement up to 120 % for strained Si/ Si0.70Ge0.30, in accordance with best experimental data. The effect of the strained Si channel thickness is also investigated: when decreasing the thickness, a mobility degradation is observed under low effective field only. The role of the different scattering mechanisms involved in the strained Si/ Si1-xGex MOS structures is explained. In addition, comparison with experimental results is discussed in terms of SiO2/ Si interface roughness, as well as surface roughness of the SiGe substrate on which strained Si is grown.Comment: 25 pages, 8 figures, 1 table, revised version, discussions and references adde

Field Dependence of Electron Velocity in High-Purity Germanium at Cryogenic Temperatures

International audienceThe electron velocity in high‐purity germanium at 20 mK has been measured as a function of the electric field in the orientation. A new simulation code, taking into account the key phenomena of ionized impurity and inelastic phonon scattering, has been developed for Monte Carlo modeling of electronic transport in Ge at cryogenic temperatures. The code accounts for the essential features of electron transport, including the hitherto unexplained effect of a negative differential mobility along the field orientation. Experimental data for the electron velocities at 20 mK are reproduced with a satisfactory accuracy

Initiation à la microélectronique ultime CMOS

Dans cet article, nous présentons un projet proposé en 1ère année de master et permettant d'appréhender le contexte de la microélectronique CMOS, avec en particulier les enjeux actuels de la miniaturisation des composants. Pour cela, les étudiants mettent en oeuvre des logiciels de simulation physique de transistors et pratiquent la réalisation technologique de structures élémentaires en salle blanche, objets qui sont ensuite caractérisés électriquement

Device performance and optimization of decananometer long double gate MOSFET by Monte Carlo simulation

International audienc

On the Ability of the Particle Monte Carlo Technique to Include Quantum Effects in Nano-MOSFET Simulation

International audienceIn this paper we report on the possibility to use particle-based Monte Carlo techniques to incorporate all relevant quantum effects in the simulation of semiconductor nano-transistors. Starting from the conventional Monte Carlo approach within the semi-classical Boltzmann approximation, we develop a multi-subband description of transport to include quantization in ultra-thin body devices. This technique is then extended to the particle simulation of quantum transport within the Wigner formulation. This new simulator includes all expected quantum effects in nano-transistors and all relevant scattering mechanisms which are taken into account the same way as in Boltzmann simulation. This work is illustrated by analyzing the device operation and performance of multi-gate nano-transistors in a convenient range of channel lengths and thicknesses to separate the influence of all relevant effects: significant quantization effects occurs for thickness smaller than 5 nm and wave mechanical transport effects manifest themselves for channel length smaller than 10 nm. We also show that scattering mechanisms still have an important influence in nanoscaled double-gate transistors, both in the intrinsic part of the channel and in the resistive lateral extensions