Quantum Mechanical Simulation Of Nanoscale MOSFET

As semiconductor technology continues to be aggressively scaled, dimensions of metal-oxide-semiconductor field oxide transistor (MOSFET) become of the same order as the mean free path and the dephasing length, such that quantum ballistic transport modeling become necessary for the assessment of the device performance. Numerical simulations based on the non-equilibrium Green's function (NEGF) theory provide powerful microscopic insight into nanoscale devices. It is widely applied to understand the device physics and to explore device engineering issues by the research community from both academy and industry. In this work, simulation approaches are realized, improved and assessed.In order to meet the strong computational efficiency requirements due to the growing complexity of quantum mechanical modeling, combined efforts from mathematical as well as physical perspective is imperative to reduce the heavy burden in numerical modeling. In this thesis, the Anderson mixing method which is a technique for fast solution of strongly coupled equations in nonlinear mathematics is introduced in the simulation flow. Adequate acceleration of the widely used predictor-corrector iteration scheme is presented.Two-dimensional quantum mechanical simulation of MOSFET device in real space is needed to study the gate leakage current. Based on the recursive Green's function (RGF) algorithm, it is developed and applied to understand the gate contact carrier injection and to explore engineering issues of gate dielectric materials.Contact block reduction (CBR) method and the RGF method are both popular techniques for numerical quantum transport simulations. The relevance and practical importance of high order Green's function elements in the standard RGF-method is presented with a comparison study using double gate MOSFET as a vehicle. Conclusions about efficiency and accuracy are drawn which offer a necessary measure on the applicability of the two methods.To summarize, this thesis is focused on the quantum mechanical numerical simulation approaches of nanoscale semiconductor devices and the efficiency, accuracy and applicability of different methods serve as the main subjects.