Dielectric Engineering of HfO 2 Gate-Stacks for Normally-ON GaN HEMTs on 200-mm Silicon Substrates

We report on the band offset and interfacial electronic properties of e-beam evaporated HfO 2 gate dielectrics on III-nitride device stacks on Si. A conduction band offset of 1.9 eV is extracted for HfO 2 /GaN along with a very low density of fixed bulk and interfacial charges for optimally annealed samples. Normally-ON HfO 2 /AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors exhibit negligible shifts in threshold voltage, transconductances of 120 mS/mm for 3- $\mu \text{m}$ gate length devices, and three-terminal off-state gate leakage currents of 55 nA/mm at a ${V}_{D}$ of 100 V. Dynamic capacitance dispersion measurements in the temperature range of 25 °C–200 °C show two peaks at the AlGaN/GaN interface corresponding to slow and fast interface traps with a peak ${D}_{\text {it}}$ of ${5.5}\times {10}^{13}$ and ${1.5} \times {10}^{13}$ eV −1 cm −2 respectively as a function of Fermi level position above ${E}_{C}$ . The HfO 2 /AlGaN interface exhibits a reasonably constant peak ${D}_{\text {it}}$ of ${2} \times {10}^{13}$ – ${4.4} \times {10}^{13}$ eV −1 cm −2 at trap levels of 0.42–0.72 eV below ${E}_{\text {C}}$ . Hysteretic pulsed $I_{D}$ – $V_{G}$ measurements revealed a negative shift in threshold voltages indicative of unoccupied donor-like trap states at the HfO 2 /AlGaN interface and comparable ${D}_{\text {it}}$ to that inferred from conductance measurements.