High-peak-power gallium arsenide oscillators

The Gunn effect appears to be the first semiconductor phenomenon capable of generating high peak power at microwave frequencies. This paper describes some preliminary experimental work in which gallium arsenide oscillators were made and operated in the range from 725 to 2000 Mc/s. Two device fabricating techniques and two circuit configurations have been found useful. Individual devices can be made to tune over a 25 percent range with a single capacitor adjustment. Voltage tuning of a few percent is generally observed. The highest peak power observed so far is 205 watts at 1540 Mc/s, obtained from two GaAs wafers operating in parallel. A large number of single devices have worked at power levels between 40 and 100 watts, and efficiencies from 3 to 9 percent. The phenomenon shows considerable promise for moderate power pulsed microwave oscillators. Predictable devices and useful design techniques will be delayed until the reproducibility and temperature variations of the raw material are brought under control.