Temperature-Dependent Current Dispersion Study in β-GaO FETs Using Submicrosecond Pulsed I-V Characteristics

A comprehensive study of drain current dispersion effects in β-Ga2O3 field-effect transistors (FETs) has been done using dc and pulsed measurements. Both the virtual gate effect in the gate-drain access region and mobile traps under the gate are the most plausible explanations for the experimentally observed pulsed current dispersion and high-temperature threshold voltage shift, respectively. Unpassivated devices show significant current dispersion between dc and pulsed I-V response in gate lag measurements characterized by time constants in the range of 400-690 μs both at room temperature and higher temperatures. The increasing time constant with temperature suggests a complex electron capture and emission process in the virtual gate. The reactive ion etching step during the device fabrication is most likely responsible for introducing the traps. The effect of traps can be minimized by using surface passivation layers, in this case, silicon nitride, which shows significant improvement in the current dispersion. This work demonstrates the detrimental effect that the traps can have on the current dispersion, which significantly limits the high-frequency operation of the device.