Temperature dependent pulsed IV and RF characterization of β-(AlxGa1−x)2O3/Ga2O3 hetero-structure FET with ex situ passivation

Abstract

In this work, we report a study of the temperature dependent pulsed current voltage and RF characterization of β-(AlxGa1−x)2O3/Ga2O3 hetero-structure FETs (HFETs) before and after silicon nitride (Si3N4) passivation. Under sub-microsecond pulsing, a moderate DC-RF dispersion (current collapse) is observed before passivation in gate lag measurements, while no current collapse is observed in the drain lag measurements. The dispersion in the gate lag is possibly attributed to interface traps in the gate–drain access region. DC-RF dispersion did not show any strong dependence on the pulse widths. Temperature dependent RF measurements up to 250 °C do not show degradation in the cutoff frequencies. After Si3N4 deposition at 350 °C, a shift of the threshold voltage is observed which changed the DC characteristics. However, the current collapse is eliminated; at 200 ns pulse widths, a 50% higher current is observed compared to the DC at high drain voltages. No current collapse is observed even at higher temperatures. RF performance of the passivated devices does not show degradation. These results show that ex situ deposited Si3N4 is a potential candidate for passivation of β-(AlxGa1−x)2O3/Ga2O3 HFETs.