Dielectric Engineering of HfO2 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-μm 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
_it
of 5.5 × 10
¹³
and 1.5 × 10
¹³
eV
^-1
cm
^-2
respectively as a function of Fermi level position above EC. The HfO
₂
/AlGaN interface exhibits a reasonably constant peak D
_it
of 2 × 10
¹³
-4.4 × 10
¹³
eV
^-1
cm
^-2
at trap levels of 0.42-0.72 eV below EC. Hysteretic pulsed ID-VG measurements revealed a negative shift in threshold voltages indicative of unoccupied donor-like trap states at the HfO
₂
/AlGaN interface and comparable D
_it
to that inferred from conductance measurements.