Novel Process for Reduced Dispersion Effects in AlGaN/GaN HEMTs

James Gillespie, Antonio Crespo, Robert Fitch, Gregg Jessen, Derrick Langley, Neil Moser, Dave Via, Matthew Williams, Mark Yannazzi 
Air Force Research Laboratory, 2241 Avionics Circle, Wright-Patterson AFB, Ohio

Effects of early deposition of Si3N4 passivation of AlGaN/GaN HEMTs have been studied as it relates to RF dispersion, breakdown voltage and X-band power.  Two AlGaN/GaN epitaxial wafers grown on SiC substrates together in one lot were used.  These wafers were processed using a common process with one exception.  One wafer had Si3N4 deposited before processing began while the other one was processed using a standard passivation process after gate deposition.  The results show improved rf dispersion characteristics (< 5% Idss reduction), higher breakdown voltages (40 volts) and superior power results (> 8.4W/mm @ 33% PAE) for the wafer which had early deposition of Si3N4 passivation. 

Keywords:  AlGaN/GaN, HEMT, Passivation, Dispersion

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