Search

This paper presents a simulation study using a novel distributive quasi-ballistic drift diffusion (DD) TCAD model applied to low mobility unstressed and high mobility stressed scaled pMOS devices. The model is implemented in a DD simulator and used to study the gate length dependence of current drives. The new model captures the physically correct potential distribution and gives the correct drive current limit in ballistic devices for both linear current response and current saturation source–drain bias conditions. The diffusive and ballistic transport is connected using a ballistic probability, which relates to the fundamental time scale in the problem—the mean energy relaxation time. The model captures the ballistic velocity degradation from the diffusive limit at linear source–drain biases. It is shown that the DD simulation with the distributive quasi-ballistic model describes the stress ballistic drive gains at high driving field, which are missed by the existing ballistic models. [ABSTRACT FROM AUTHOR]

We present quantum transport simulation results for InAs and In0.7Ga0.3As double-gate MOSFETs by using an atomistic full-band basis to evaluate the tunneling currents in the OFF state. While InAs has the advantage of lower mass and higher injection velocity, it also has lower bandgap. For low gate bias, the overlap in energy of the valence band in the channel with the source/drain conduction bands results in band-to-band tunneling (BTBT) between source and drain, which clamps the OFF current. Such current can be reduced by increasing the bandgap of the material either by increasing confinement or by lowering the In content, for example, using In0.7Ga0.3As. Grading the doping of the source/drain region to create a wider barrier also reduces BTBT, but to a lesser extent. [ABSTRACT FROM PUBLISHER]

We present a compact model to calculate the capacitance of undoped high-mobility low-density-of-states materials in double-gate device architecture. Analytical equations for estimating the subband energies, while taking the effect of wavefunction penetration into the gate oxide and the effective mass discontinuity, are presented for the first time in a compact modeling framework. The surface potential equation for a two subband system is solved, assuming Fermi–Dirac statistics, and compared to numerical Schrodinger–Poisson simulations. The importance of accurately treating the charge profile distribution is illustrated, and an analytical expression for the effective oxide thickness to model the charge centroid is developed. [ABSTRACT FROM AUTHOR]