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We extract the electric properties of border traps with long time constant in low-pressure chemical vapor deposition (LPCVD) Si3N4/GaN/AlGaN/GaN metalâ€"insulatorâ€"semiconductor (MIS) structure using quasi-static capacitance voltage method. The energy and depth distribution of the border traps is calculated based on the analysis of energy band diagram and charging dynamic of border traps in the MIS structures. With this method, it is found that LPCVD Si3N4/GaN/AlGaN/GaN MIS structure have a high density of border traps in the order up to 1021 cmâˆ'3 eVâˆ'1 located at energy level between E C,GaN âˆ' 0.04 eV and E C,GaN âˆ' 0.66 eV with distance of 1.0â€"4.2 nm from the Si3N4/GaN interface. Microstructure analysis suggests that the high density of border traps is possibly correlated to the oxygen content at the Si3N4/GaN interface. Meanwhile, the proposed method is also suitable for MIS or metal-oxide-semiconductor structure on other semiconductors, providing another powerful tool to analysis the physical properties of border traps. [ABSTRACT FROM AUTHOR]

We report the effect of the gate recess process and the surface of as-etched GaN on the gate oxide quality and first reveal the correlation between border traps and exposed surface properties in normally-off Al2O3/GaN MOSFET. The inductively coupled plasma (ICP) dry etching gate recess with large damage presents a rough and active surface that is prone to form detrimental GaxO validated by atomic force microscopy and X-ray photoelectron spectroscopy. Lower drain current noise spectral density of the 1/f form and less dispersive ac transconductance are observed in GaN MOSFETs fabricated with oxygen assisted wet etching compared with devices based on ICP dry etching. One decade lower density of border traps is extracted in devices with wet etching according to the carrier number fluctuation model, which is consistent with the result from the ac transconductance method. Both methods show that the density of border traps is skewed towards the interface, indicating that GaxO is of higher trap density than the bulk gate oxide. GaxO located close to the interface is the major location of border traps. The damage-free oxidation assisted wet etching gate recess technique presents a relatively smooth and stable surface, resulting in lower border trap density, which would lead to better MOS channel quality and improved device reliability. [ABSTRACT FROM AUTHOR]

In this study, the physical properties of F ion-implanted GaN were thoroughly studied, and the related electric-field modulation mechanisms in ion-implanted edge termination were revealed. Transmission electron microscopy results indicate that the ion-implanted region maintains a single-crystal structure even with the implantation of high-energy F ions, indicating that the high resistivity of the edge termination region is not induced by amorphization. Alternately, ion implantation-induced deep levels could compensate the electrons and lead to a highly resistive layer. In addition to the bulk effect, the direct bombardment of high-energy F ions resulted in a rough and nitrogen-deficient surface, which was confirmed via atomic force microscopy (AFM) and X-ray photoelectron spectroscopy. The implanted surface with a large density of nitrogen vacancies can accommodate electrons, and it is more conductive than the bulk in the implanted region, which is validated via spreading resistance profiling and conductive AFM measurements. Under reverse bias, the implanted surface can spread the potential in the lateral direction, whereas the acceptor traps capture electrons acting as space charges, shifting the peak electric field into the bulk region in the vertical direction. As a result, the Schottky barrier diode terminated with high-energy F ion-implanted regions exhibits a breakdown voltage of over 1.2 kV., Competing Interests: The authors declare that they have no conflicts of interest in this work., (© 2021 The Authors. Publishing Services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.)