Simultaneous enhancement of current and breakdown voltage in AlGaN / GaN MOSHEMTs using sputtered / PECVD gate-dielectrics

A new SiO₂-deposition scheme combining radio frequency (rf) magnetron sputtering and plasma enhanced chemical vapor deposition (PECVD) has been developed to produce gate-SiO₂ for GaN-based metal-oxide-semiconductor high-electron-mobility-transistors (MOSHEMTs). The high-density sputtered-SiO₂ was employed to suppress the gate leakage current while the low-density PECVD-SiO₂ was used to protect the sputtering damage, and also to increase the drain current via stress-induced-polarizations. Thus-obtained MOSHEMT exhibited a drain current of over 100 mA and a gate leakage current of 4.2 nA/mm. A high breakdown voltage of 634 V was achieved for a short gate-drain length of 6 μm, showing the promise of the new SiO₂-deposition scheme for the fabrication of GaN-based MOSHEMTs for high-power applications.