Subband decomposition approach for the simulation of quantum electron transport in nanostructures

The modeling of ballistic quantum transport in ultimate size semiconductor devices usually involves a self-consistent solution between the Schrödinger and the Poisson equations. In the 2D or 3D real space, this procedure requires huge computer resources to obtain the I–V characteristics. The general approach proposed in this article relies on the decomposition of the wave function on subband eigenfunctions, which account for the confinement of the electrons in the whole structure. The method can be applied to study large 2D and 3D real systems with a drastic reduction of the numerical cost, since the dimension of the transport problem for the Schrödinger equation is now reduced in real space. The results obtained for the 2D nanoscale MOSFETs show the efficiency of the algorithm and allow to estimate the effects of the coupling between the subbands. The asymptotic approach of the subband decomposition is also presented for devices showing a strong confinement for the electron gas as the 3D electron waveguide devices.