TCAD-Based Assessment of Dual-Gate MISHEMT with Sapphire, SiC, and Silicon Substrate

Abstract

ABSTRACT This paper examines the DC performance of Dual-Gate MISHEMT with different substrate material such as sapphire, silicon carbide SiC, and silicon. The performance parameters evaluated are threshold voltage, drain current, transconductance, and drain conductance. It is observed that DG-MISHEMT with the sapphire substrate and HfO2 gate dielectric results in positive threshold voltage shift from −4.7 to −3.8 V(∼19%) and also degrades the drain current as compared to the device with silicon nitride gate dielectric due to the reduced channel charge concentration. But the device with HfO2/Al2O3 gate stack maintains 182 mA/mm of IDS along with a positive threshold voltage shift of 14.8% as compared to DG-MISHEMT with Si3N4 gate dielectric and sapphire substrate. A similar performance has been observed with Dual-Gate MISHEMT with SiC and silicon substrate. The device, having the silicon substrate and HfO2/Al2O3 gate stack, shows a positive threshold voltage shift of ∼53%, but as a trade-off the drain current reduces to 158 mA/mm as compared to 183 mA/mm of the device at low drain bias with the sapphire substrate and Si3N4 gate dielectric.