Novel composite contact design and fabrication for planar Gunn devices for millimeter-wave and terahertz frequencies

Contacts to planar Gunn devices on the semiconductor surface suffer from high electric field stress and current crowding leading to premature burn out. We have developed a new composite contact design using a Schottky extension of the conventional Ohmic contact. The composite contact structures have been fabricated and tested to mitigate the effects of high concentrations of charge and high electric fields at the anode edge of the planar Gunn diode. Monte Carlo simulations confirm these experimental results in composite contacts. These results suggest a mechanism of increased lifetime when using composite contacts as compared to conventional Ohmic contacts. This is of significant importance for planar Gunn device operation at millimetre wave and terahertz frequencies where high doping density (similar to 10(17) cm(-3)) and short cathode to anode separation (1 mu m or less) is required. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim