Enhanced device performance of AlGaN/GaN HEMTs using HfO2 high-k dielectric for surface passivation and gate oxide

AlGaN/GaN high electron mobility transistors (HEMTs) using HfO2 as a surface passivation layer and metal-oxide-semiconductor HEMTs (MOS-HEMTs) using HfO2 as gate oxide have been investigated and compared with the regular HEMTs. In MOS-HEMTs, the HfO2 gate dielectric is also used for passivation simultaneously. Our measurements have shown that both passivated HEMTs and MOS-HEMTs outperformed the regular HEMTs in dc, high-frequency and pulsed-mode operations, with MOS-HEMTs exhibiting the best characteristics, including the highest drain current, the lowest gate leakage current, the largest gate voltage swing, the highest cut-off frequencies and the best immunity to current collapse. In addition, the decrease in transconductance of MOS-HEMTs relative to HEMTs is as low as 8.7%, most probably a consequence of the high-k value of HfO2. Our results thus indicate the great potential of HfO/AlGaN/GaN MOS-HEMTs for high-frequency and high-power applications.