Mapping of interface traps in high-performance Al2O3/AlGaN/GaN MIS-heterostructures using frequency- and temperature-dependent C-V techniques

With an in situ low-damage NH₃-Ar-N₂ plasma pre-gate treatment, a high-quality Al₂O₃/GaN-cap interface has been obtained in the Al₂O₃/GaN/AlGaN/GaN MIS-structures. Frequency- and temperature-dependent C-V characterization techniques were developed to map the interface trap density (D_it) at the dielectric/III-nitride interface, whereby a low D_it of ~10¹²-10¹³ cm^-2eV^-1 in the Al₂O₃/GaN/AlGaN/GaN MIS-structures was extracted. The mechanism for the high-quality interface was validated to be effective removal of native oxide and the subsequent formation of a monocrystal-like nitridation inter-layer on the GaN surface. Both D_it mapping and the pre-gate treatment techniques are of significance for the improvement of III-nitride MIS-HEMTs.