A quantum drift-diffusion model and its use into a hybrid strategy for strongly confined nanostructures (Q1728012)

The paper deals with the problem of developing computationally efficient models that describe with accuracy the electron transport in nanoelectronics. A formal derivation of a Quantum Drift-Diffusion (QDD) model is proposed, which relies on an extension of Levermore's moment approach to quantum systems. The starting point is an effective mass model, obtained by considering the crystal lattice as periodic only in the one dimensional longitudinal direction and keeping an atomistic description of the entire two dimensional cross-section. It consists of a sequence of one dimensional device dependent Schrödinger equations, one for each energy band, in which quantities retaining the effects of the confinement and of the transverse crystal structure are inserted. These quantities are incorporated into the definition of the entropy. Consequently the obtained QDD model has a peculiar quantum correction that includes the contributions of the different energy bands. Further, in order to simulate the electron transport in a gate-all-around Carbon Nanotube Field Effect Transistor, a spatial hybrid strategy coupling the QDD model in the Source/Drain regions and the Schrödinger equations in the channel is proposed. Self-consistent computations are performed coupling the hybrid transport equations with the resolution of a Poisson equation in the whole three dimensional domain.