Transient characteristics of AlxGa1-xN/GaN heterojunction field-effect transistors

Transient characteristics of drain-source current in response to picosecond pulsed gate-source voltages in AlxGa1-xN/GaN heterojunction field-effect t ransistors (HFETs) have been measured. It was found that the switching time constants were of the order of tens of picoseconds and depended strongly o n the gate-source bias V-GS as well as drain-source bias V-DS. Slow transie nts caused by charge trapping effects such as those observed in AlGaAs/GaAs HFETs were absent in AlGaN/GaN HFETs. Our results suggested that the depen dence of the effective electron mobility on the sheet density dictates the overall drain current transient characteristics as well as the device switc hing speed of AlGaN/GaN HFETs. (C) 2000 American Institute of Physics. [S00 03-6951(00)01251-1].