Influence of SiO/sub 2/ and Si/sub 3/N/sub 4/ passivation on AlGaN/GaN/Si HEMT performance

The different influences of SiO/sub 2/ and Si/sub 3/N/sub 4/ passivation on the performance of AlGaN/GaN/Si HEMTs are reported. DC characteristics are less enhanced by using SiO/sub 2/ than Si/sub 3/N/sub 4/. This is in agreement with carrier concentration changes after passivation, as follows from Hall data. Small signal RF performance is degraded after applying SiO/sub 2/ and enhanced after Si/sub 3/N/sub 4/ passivation, e.g. for unpassivated devices f/sub T//spl cong/17 GHz which decreases to 9 GHz and increases to 28 GHz for SiO/sub 2/ and Si/sub 3/N/sub 4/, respectively. The f/sub max//f/sub T/ ratio does not change after passivation.