Positive Shift in Threshold Voltage for Reactive-Ion- Sputtered Al2O3/AlInN/GaN MIS-HEMT

AlInN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) have been fabricated with reactive-ion-sputtered (RIS) Al
₂
O
₃
as a gate dielectric. Significant reduction in the gate leakage current is achieved upon insertion of RIS-Al
₂
O
₃
. MIS-HEMTs also show better transconductance, drain characteristics, and ION/IOFF ratio. Most interestingly, a positive shift in threshold voltage is observed for MIS-HEMTs indicating the presence of net negative charge at oxide-semiconductor interface. The origin and stability of the negative charge at the interface is discussed in this letter.