Abstract

Band-gap engineering is a new powerful technique to design heterojunction devices. Using the rules of band-gap engineering new band diagrams with nearly arbitrary and continuous band gap variations can be constructed.^1,2 This, along with the present capabilities of MBE and MOCVD growth techniques, has led to a new class of optoelectronic and electron devices and superlattice materials. These include among others multilayer avalanche photodiodes, staircase solid-state photomultipliers, phototransistors with graded gap base, and pseudoquaternary semiconductors. In addition, heterojunction band discontinuities can be artificially tuned using doping interface dipoles. This new technique has tremendous potential for novel semiconductor devices.³ Finally recent results on a new class of high detectivity, high gain, low voltage superlattice photoconductors (effective mass filters) are discussed. These devices are based on a newly discovered quantum-type photoconductivity. The high photoconductive gain is caused by the large difference between the tunneling rates of electrons and holes in a superlattice (effective mass filtering).

© 1985 Optical Society of America