effmass: An effective mass package

Abstract

Many semiconductor properties depend on the response of electrons to an external pertubation. This perturbation could take the form of an electric field, change in temperature or an applied lattice stress. In a crystal, this response depends on the interaction of the electrons with a periodic potential. The effective mass approximation assumes that the response of an electron in a periodic potential is equivalent to that of a free electron with a renormalised mass (called the "effective mass"). This makes the effective mass a critical parameter in models for the optical and transport properties of a semiconductor.