Impact of surface treatment under the gate on the current collapse of unpassivated AlGaN/GaN heterostructure field-effect transistors

Unpassivated GaN/AlGaN/GaN/SiC heterostructure field-effect transistors were fabricated on intentionally undoped and 5 x 10(18) cm(-3) modulation-doped material structures. The influence of surface treatment before gate metallization on the gate leakage and drain current collapse of the devices was observed. In the case of a short HCl treatment (similar to 5 s), a relatively small gate leakage ( 10(-4) A mm(-1)) and a simultaneously negligible current collapse (< 5%). This effect is qualitatively similar in devices prepared on the undoped and doped heterostructures. It is assumed that a thin interfacial oxide layer under the gate might be responsible for a lower leakage current and a larger current collapse of the devices