Local-oscillator-induced noise in GaAs Schottky mixer diodes

Increased noise temperature induced by local-oscillator power has been measured in Schottky-diode millimetre-wave mixers at 250 MHz and 4.75 GHz. Electric-field calculations indicate a portion of this noise is due to intervalley scattering in the undepleted epitaxial layer directly adjacent to the Schottky-diode anode. A noise-temperature equation is presented, which accounts for both shot and thermal noise, where the thermal portion includes the intervalley scaltering component.