Technology towards GaAs MESFET-based IC for high temperature applications

A GaAs MESFET technology for the fabrication of devices, specially developed for continuous, reliable operation at high temperatures is presented. The technology is based on highly stable ohmic and Schottky contacts containing WSiN diffusion barriers and is optimized towards minimum temperature induced leakage currents across the substrate or along the semiconductor surface. The isolation of individual devices on chip is accomplished by multiple implantations of O+ -ions at different energies. Drain/source leakage currents at high temperatures are significantly reduced due to the use of GaAs epitaxial MESFET wafers with an AlAs/GaAs superlattice structure followed by a p−-buffer. MESFETs, fabricated by using this technology, have been optimized to match the requirements for continuous operation at high temperatures up to 300 °C and have been successfully implemented in high temperature MMICs. Microwave circuits such as mixers, buffer amplifiers and voltage controlled oscillators aswell as operational amplifiers have been realized and characterized at temperatures up to 300 °C.