Improving off-state leakage characteristics for high voltage AlGaN/GaN-HFETs on Si substrates

Abstract

We present a reliable process and design technique for realizing high voltage AlGaN/GaN hetero-junction field effect transistors (HFETs) on Si substrates with very low and stable off-state leakage current characteristics. In this work, we have investigated the effects of the surface passivation layer, prepared by low pressure chemical vapor deposition (LPCVD) of silicon nitride (SiNx), and gate bus isolation design on the off-state leakage characteristics of metal–oxide–semiconductor (MOS) gate structure-based GaN HFETs. The surface passivated devices with gate bus isolation fully surrounding the source and drain regions showed extremely low off-state leakage currents of less than 20nA/mm at 600V, with very small variation. These techniques were successfully applied to high-current devices with 80-mm gate width, yielding excellent off-state leakage characteristics within a drain voltage range 0–700V.