Poly-silicon CMOS compatible gate module for AlGaN/GaN-on-silicon MIS-HEMTs for power electronics applications

In this paper we present a new poly-silicon gate process for AlGaN/GaN MIS-HEMT power transistors. Using a complete metal-free front-end processing of the gate module the process is fully CMOS compatible. Additionally, the gate reliability can be significantly increased. We used a three-step LPCVD SiN passivation fully enclosing the gate electrode made of polycrystalline silicon. As gate dielectrics LPCVD deposited SiN are used with a thickness of 20nm and 120nm. We compared these devices with MIS-HEMTs using Al as gate electrode. Constant current measurements have been performed that show with Q(BD,poly,20) nm=714 C/cm2 and a MTTF(0.5A/cm2) =1293s significant higher charge pumping capability through the gate for the poly-Si gated devices compared to conventional metal gates.