Active Microwave Semiconductor Devices

This paper presents a survey of active microwave semiconductor devices with emphasis on devices made from Gallium Arsenide which is presently the material with the greatest scope and promise. Thanks to the three properties of high mobility, low threshold field and the existence of semi-insulating substrate GaAs is now preferably used as the starting material for avalanche (IMPATT) diodes, transferred electron (Gunn) diodes and field effect transistors. The GaAs IMPATT diode is presently the hottest performer in the frequency range up to X-band, whereas at higher frequencies the double-drift Si IMPATT diode still has the honor of maximum power and efficiency. Although exhibiting lower power and efficiency the Gunn diode has certain advantages such as low noise, low bias voltage, needs less critical tuning and bias circuitry and has a simpler structure. During recent years the GaAs field effect transistor has been developed to the fastest three terminal semiconductor device with outstanding noise performance. The paper outlines the basic device physics, terminal characteristics and reports the newest results.