Perhydropolysilazane spin-on-dielectric passivation buffer layers for AlGaN/GaN high-electron mobility transistors

Perhydropolysilazane spin-on-dielectric (SOD) is examined as a SiO _x buffer for the plasma-enhanced CVD (PECVD) Si ₃N ₄ passivation of AlGaN/GaN high-electron-mobility transistors (HEMTs). Compared to HEMTs passivated by the conventional PECVD Si ₃N ₄, the SOD-buffered structure shows about two times greater saturation drain current. From the modified charge control model and Silvaco device simulation, it is proposed that this ehancement is due to the minimised plasma-induced surface states in the SOD-buffered structure compared to a high density (∼5×10 ¹²/cm ²) of negatively charged states in the PECVD Si ₃N ₄ passivation structure.