Massive Interminiband Transitions Triggered by Strong Static Electric Fields in Superlattices

Abstract

The recent experimental observations of Bloch oscillations and the emission of electromagnetic radiation1 in the terahertz regime in semiconductor superlattices subject to static uniform electric fields, suggest that these systems may be developed as useful THz generators. The Bloch period is given by τB = h/(eFa), where e and F denote the magnitude of the electron charge and the electric field, h is Planck’s constant, and a is the spatial period of the superlattice. Modeling these systems in terms of independent electrons in an idealized one-dimensional superlattice potential in the effective mass approximation, and using high-accuracy numerical methods to solve the time-dependent Schrodinger equation, the electron wave function has been found2–4 to exhibit long-lived Bloch oscillations for electric fields in the range used in experiment. We here present results for this model, obtained using the methods of Ref 2–4, for the regime where the electrons are subject to very strong static electric fields, so that they exhibit characteristics of acceleration as well as some residual but faint signs of Bloch oscillations. Some preliminary results for this regime have been given in Sec. IIID of Ref 3, while a very detailed analysis is presented in Ref 4.