Hot-electron reliability improvement using perhydropolysilazane spin-on-dielectric passivation buffer layers for AlGaN/GaN HEMTs

•We fabricate AlGaN-GaN HEMT with the spin-on-dielectric (SOD) buffer layer.•The SOD buffers minimize surface states at the passivation interface.•Enhanced drain current characteristic is obtained from the SOD-buffered HEMTs.•The SOD-buffered structure also greatly improves device reliability.

We investigate the effects of perhydropolysilazane spin-on-dielectric (SOD) buffer layer adopted prior to Si3N4 passivation on the dc drain current level and degradation after the electrical stress in the AlGaN-GaN high electron mobility transistors (HEMTs). The SOD-buffered HEMTs show ∼1.6 times greater drain current densities (∼257 mA/mm) than those of the devices with conventional-Si3N4 passivations (∼155 mA/mm). After the hot electron stresses (step-wise and constant) applied to the devices, it is also found that the SOD-buffered structure produces greatly improved device reliability in terms of the dc current collapse (15% for step-stress and constant stress) compared to the conventional structure (25% for each case). We propose that the enhancement of SOD-buffered structure in dc current collapse is due to the reduction in surface state density at the passivation interface and the suppressed electron trapping.