Origin and elimination method of parasitic gate leakage current for AlGaN/GaN heterostructure field effect transistor

The Schottky gate leakage current of AlGaN/GaN HFET was systematically investigated. Experimental results were acquired from gates of HFET and from round diodes on the same wafer. The performed analysis clearly shows that HFET gate current behaves according to additional physical mechanism. Hypothesis, that the source of parasitic leakage is the contact point between gate metal and two dimensional electron gas on the mesa edges, was theoretically and experimentally proved. Cost effective technological solution with SiO2 “patch” layer is presented. Transistors, manufactured with “patch” layer, have higher breakdown, two orders of magnitude lower gate leakage current, excellent performance and should be more reliable. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)