The discretized Schrodinger equation and simple models for semiconductor quantum wells

Timothy B. Boykin, Electrical and Computer Engineering, University of Alabama
Gerhard Klimeck, Jet Propulsion Laboratory, California Institute of Technology; Network for Computational Nanotechnology, Purdue University

Abstract

The discretized Schr¨odinger equation is one of the most commonly employed methods for solving one-dimensional quantum mechanics problems on the computer, yet many of its characteristics remain poorly understood. The differences with the continuous Schr¨odinger equation are generally viewed as shortcomings of the discrete model and are typically described in purely mathematical terms. This is unfortunate since the discretized equation is more productively viewed from the perspective of solid-state physics, which naturally links the discrete model to realistic semiconductor quantum wells and nanoelectronic devices. While the relationship between the discrete model and a one-dimensional tight-binding model has been known for some time, the fact that the discrete Schr¨odinger equation admits analytic solutions for quantum wells has gone unnoted. Here we present a solution to this new analytically solvable problem. We show that the differences between the discrete and continuous models are due to their fundamentally different bandstructures, and present evidence for our belief that the discrete model is the more physically reasonable one.