ABSTRACT
Active device operation is strongly dependent upon the charge transport, thermal, electronic breakdown, and mechanical characteristics of the semiconductor material from which the device is fabricated. The IMPact Avalanche Transit-Time (IMPATT) diode, transferred electron device, and tunnel diode are the most commonly used two-terminal active devices. IMPATT and Gunn diodes require a combination of charge injection and transit time effects to generate active characteristics and they operate as negative immittance components. Transferred Electron Devices are widely used in oscillators from the microwave through high mm-wave frequency bands. They can be fabricated at low cost and provide an excellent price-to-performance ratio. The IMPATT and Gunn diodes make use of internal feedback resulting from electronic charge transfer within the semiconductor structure. Tunnel diodes are limited in operation frequency by the time it takes for charge carriers to tunnel through the junction.
