The variably spaced superlattice energy filter

Abstract

A new superlattice device concept which provides for high energy injection of electrons into a semiconductor layer is presented. The device is based on resonant tunneling of electrons between adjacent aligned quantum well levels in a variably spaced superlattice structure. By a judicial choice of well and barrier widths the energy levels under reverse bias become aligned such that resonant tunneling of electrons through the structure can occur. Thus, electrons are injected into a semiconductor layer at an energy corresponding to the energy of the first subband in the last quantum well. This structure has significant advantages over the conventional method of producing hot electrons in that a nearly monoenergetic high-energy electron distribution is created at low reverse bias and with high efficiency, since energy loss to phonons is inhibited as a consequence of the channeling of electrons through a narrow band of quantum states. Applications of the VSSEF structure to avalanche photodiodes, IMPATT diodes and electroluminescent devices are discussed.