Comparison of different surface passivation dielectrics in AlGaN/GaN heterostructure field-effect transistors

Different dielectrics were used for post-processing surface passivation of AlGaN/GaN heterostructure field-effect transistors (HFETs) and the resulting electrical characteristics examined. An increase in the maximum drain current of approximately 25 percent was observed after Si3N4 and SiO2 deposition and about 15 percent for annealed SiO on AlGaN/GaN HFETs. In all cases, the passivation was found to increase the gate leakage current with an observed reduction in the leakage activation energy. However, the rise in gate leakage current was least for SiO. The plasma enhanced chemical vapor deposition method was found not to contribute to the passivation mechanism, while the presence of Si appears to be an important factor. (Author)