Concepts For Electron-Beam And Optical Control Of Bulk Semiconductor Switches

Abstract

Two concepts for externally controlled bulk semiconductor switches are discussed. One concept is based on electron-beam ionization of direct semiconductors with a negative differential electron mobility region in their velocity-field strength characteristic (e.g. GaAs). The e-beam is injected through one of the contacts in direction of the applied electric field, similar to e-beam controlled diffuse discharge switches1. Because of the very high value of the source function (number of electrons generated per second and cubic centimeter) compared to diffuse discharge switches, the ratio of switch current to sustaining e-beam current can reach values of 105. Generation of excess charge carriers in the region beyond the range of the electrons is provided by absorption of recombination radiation and bremsstrahlung emanating from the e-beam excited zone. Opening of the switch is obtained by turning the e-beam off. If the switch is part of an inductive discharge circuit, the increasing field strength during opening drives the semiconductor through a negative differential mobility region into a low conductivity range, a mechanism which supports switch opening. A second switch concept is based on optical control of semiconductors, where lasers are used to drive the switch into and out of the conductive state using two different wavelengths. The direct semiconductor is doped with material which generates deep acceptor levels and is compensated with donors in shallow levels. Increase of conductivity - closing of the switch - is obtained through excitation of electrons from the occupied deep traps. Reduction of conductivity - opening of the switch - is achieved through optical hole excitation from the deep centers and subsequent direct recombination of electron-hole pairs.© (1987) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.