Low-Leakage-Current AlN/GaN MOSHFETs Using for Increased 2DEG

摘要

Metal-oxide-semiconductor heterostructure field effect transistors (MOSHFETs) were fabricated with an AlN/GaN heterostructure grown on Si substrates. A 7-nm $hbox{Al}_{2}hbox{O}_{3}$ serving as both gate dielectric under the gate electrode and passivation layer in the access region was used. It was found that the $hbox{Al}_{2}hbox{O}_{3}$ was superior to $hbox{SiN}_{x}$ in increasing the 2-D electron gas (2DEG) density and thereby reducing the access resistance. In addition, the off -state leakage current $(I_{rm off})$ in these AlN/GaN MOSHFETs was reduced by four orders of magnitude to $hbox{7.6} times hbox{10}^{-5} hbox{mA/mm}$ as a result of the $hbox{Al}_{2} hbox{O}_{3}$ gate dielectric, compared to that of AlN/GaN HFETs. Meanwhile, the subthreshold slope was improved to a nearly ideal value of 62 mV/dec because of the extremely low $I_{rm off}$. The MOSHFETs with 1-$muhbox{m}$ gate length exhibited good DC characteristics. A maximum drain current of 745 mA/mm and a peak extrinsic transconductance of 280 mS/mm were achieved.