Abstract
Accumulation-type GaN metal-oxide-semiconductor field-effect-transistors (MOSFET's) with atomic-layer-deposited HfO 2 gate dielectrics have been fabricated; a 4 μm gate-length device with a gate dielectric of 14.8 nm in thickness (an equivalent SiO 2 thickness of 3.8 nm) gave a drain current of 230 mA/mm and a broad maximum transconductance of 31 mS/mm. Owing to a low interfacial density of states (D it ) at the HfO 2 /GaN interface, more than two third of the drain currents come from accumulation, in contrast to those of Schottky-gate GaN devices. The device also showed negligible current collapse in a wide range of bias voltages, again due to the low D it , which effectively passivate the surface states located in the gate-drain access region. Moreover, the device demonstrated a larger forward gate bias of +6 V with a much lower gate leakage current. © 2010 Elsevier Ltd. All rights reserved.