IMPATT diodes

The term IMPATT diode (IMPact Avalanche and Transit Time) has come to describe a class of devices with a wide number of variants, including single and double drift devices, high efficiency structures, and devices in gallium arsenide and silicon. A description is presented of the theory of IMPATT diode operation, taking into account the abrupt p-n junction single-drift diode. All IMPATT devices are reverse-biased diodes, either Schottky or p-n junctions, operating in the voltage region beyond avalanche breakdown. Under such conditions, several aspects of hot-electron theory apply which are fundamental to operation. Aspects of impact ionization are considered along with velocity saturation and the induced current from a moving charge. Attention is given to the IMPATT mechanism, Read's equation, physical limits on device performance, a comparison of materials and device structures, and a performance summary.