Effect of unintentional charges, on the performance of nanoscale DGMOSFETs

A model of the nano DGMOSFET employing Non-Equilibrium Green´s Function (NEGF) formalism is used to analyse the influence of the presence of ac stray negative charge in the channel on the perfomance of the device. As done preciously, the MOSFET is considered as essentially a 2D charge sheet, since the width of the device is very large, and the eigen vectors in that direction are effectively taken as plane waves. We then use the uncoupled mode space approach to reduce the problem to ID, enabling one to use two-dimensional electrostatics to model transport through the device. The NEGF equations and the Poisson equation are solved self-consistently to obtain subband energy and current in the device. Taking the position of the trapped charge as random, we compute its effect on the threshold voltage, sub-threshold swing, and drive current, and compare these results with that of a device having a pure channel, devoid of any such trapped charges.