IMPATT (Impact Avalanche Transit Time) Devices

Abstract

IMPATT (Impact Avalanche Transit Time) devices are solid state oscillators or amplifiers for microwave and millimeter wave frequencies up to above 200 GHz, generally with high power output (for a solid state device). Efficiencies as high as 25% have recently been obtained withGaAsdevices, but the traditional IMPATT is a silicon device with up to 15% efficiency. The basic principle involves a 180° phase-delay of the current with respect to the voltage, which clearly will make the device exhibit a negative resistance. Shockley (1954) had introduced this general idea, not yet involving impact avalanching to produce the phase-shift. A number of different p-n-junction type structures are used today. During operation, the diode is undergoing (controlled) reverse break-down.