Interface/border trap characterization of Al_2O_3/AlN/GaN metal-oxide-semiconductor structures with an AlN interfacial layer

摘要

We report the interface characterization of Al_2O_3/AlN/GaN MOS (metal-oxide-semiconductor) structures with an AlN interfacial layer. A thin monocrystal-like interfacial layer (AlN) is formed at the Al_2O_3/GaN to effectively block oxygen from the GaN surface and prevent the formation of detrimental Ga-O bonds. The suppression of Ga-O bonds is validated by X-ray photoelectron spec-troscopy of the critical interface. Frequency-dispersion in C-V characteristics has been significantly reduced, owing to improved interface quality. Furthermore, using the conventional conductance method suitable for extracting the interface trap density D_(it) in MOS structures, D_(it) in the device with AlN was determined to be in the range of 10~(11)-10~(12) eV~(-1) cm~(-2), showing one order of magnitude lower than that without AlN. Border traps near the gate-dielectric/GaN interface were identified and shown to be suppressed by the AlN interfacial layer as well.