Analysis of Off-State Leakage properties of High Electron Mobility Transistors based on AlGaN/GaN heterostructures

摘要

The off-state leakage (Ioff) properties of the AlGaN/GaN high electron mobility field-effect transistors (HEMTs) was analyzed by fabricating metal-semiconductor (MES)-HEMTs and metal-insulator-semiconductor (MIS)-HEMTs. The experimental results show that off-state gate leakage (Ig-off) for MES-HEMTs is larger than the corresponding off-state drain leakage (Id-off), which suggests that Id-off is a branch of Ig-off. Ioff by the ion implantation isolation is nearly an order of magnitude lower than that by the ICP-etching isolation, which suggests the side wall under the gate electrode caused by the etching isolation can increase the Ig-off and planar structure formed by ion implantation isolation can suppress gate leakage efficiently. A linear relationship of Id-off and Ig-off for MES-HEMTs with the gate length implies that the gate area is proportional to the Ig-off. This indicates that the edge effect on the Ig-off can be negligible. At the same time, the estimated current with Lg of 0 μm is not zero, indicating the gate metal covered isolation region participates in conduction. MIS-HEMTs can suppress Ioff significantly, indicating that the existence of the insulation layer can not only reduce the leakage current from effective gate electrode, but also suppress the leakage current from gate metal-covered isolation area.