Fabrication and Characterization of AlGaN/GaN-on-Si High Electron Mobility Transistors with p-type NiO Based Gate Stack

The p-type oxide semiconductors, such as p-NiO, can be attractive alternative for p-GaN gate stack used for normally-off GaN high electron mobility transistors (HEMTs) devices, due to simpler, low-cost, and low-thermal budget processes flow. Herein, the fabrication and characterization of AlGaN/GaN-on-Si HEMTs with p-NiO gate module is presented. It is examined in details how gate module postdeposition steps, such as annealing and passivation layers deposition, can influence the device parameters. As-fabricated devices suffer from excessive gate forward leakage current that prevent the control of current flow. However, annealing of the devices in oxygen containing atmosphere substantially improves devices parameters resulting in forward gate leakage reduction, positive threshold voltage shift, and quasi normally-off operation. The deposition of passivation layers leads to depletion-mode operation but at the same time it causes an increase in the on-state current and a decrease in on-state resistance and a further decrease in the gate forward current. Obtained results show that the influence of individual technological steps, such as annealing and passivation deposition, should be carefully examined as they have a significant impact on the parameters of the GaN-based HEMTs utilizing p-NiO as a gate material.