Low-Noise Millimeter-Wave Schottky Mixers

Recent developments in the fields of semiconductor crystal growth and thin film lithography have proven to be useful in constructing millimeter-wave Schottky mixers with very low noise temperatures. These mixers look attractive for use in short-haul communication receivers, imaging radiometers, for detection of trace molecules in the atmosphere and for radio astronomical observations. The device physics of the metal-semiconductor contact (Schottky diode) which is needed for the mixing process is discussed and novel techniques to fabricate the required junction and circuit geometries are described. Conventional and subharmonically pumped mixers built with waveguide components and stripline circuits are treated. Results of tests performed on cryogenically cooled and room temperature mixers built in the 30-300 GHz frequency range using molecular beam epitaxy diodes and conventional vapor phase epitaxy diodes are reported.