Demonstration of Wide Bandgap AlGaN/GaN Negative-Capacitance High-Electron-Mobility Transistors (NC-HEMTs) Using Barium Titanate Ferroelectric Gates

A negative-capacitance high electron mobility transistor (NC-HEMT) with low hysteresis in the subthreshold region is demonstrated in the wide bandgap AlGaN/GaN material system using sputtered BaTiO(3)as a "weak" ferroelectric gate in conjunction with a conventional SiN(x)dielectric. An enhancement in the capacitance for BaTiO3/SiN(x)gate stacks is observed in comparison to control structures with SiN(x)gate dielectrics directly indicating the negative capacitance contribution of the ferroelectric BaTiO(3)layer. A significant reduction in the minimum subthreshold slope for the NC-HEMTs is obtained in contrast to standard metal-insulator-semiconductor HEMTs with SiN(x)gate dielectrics-97.1 mV dec(-1)versus 145.6 mV dec(-1)-with almost no hysteresis in theI(D)-V(G)transfer curves. These results are promising for the integration of ferroelectric perovskite oxides with III-Nitride devices toward NC-field-effect transistor switches with reduced power consumption.