We have developed a silicon oxynitride (SiON) deposition process using a plasma-enhanced chemical vapor deposition system for the gate dielectric of GaN-on-Si metal-insulator-semiconductor field-effect transistors (MISFETs). The optimized SiON film had a relative dielectric constant of 5.3 and a breakdown field of 12 MV/cm. A normally-off GaN-on-Si MISFET fabricated with a 33-nm SiON gate dielectric exhibited a threshold voltage of ~2 V, an ON-resistance of 7.85 mQ · cm ² , and a breakdown voltage of ~640 V at the OFF-state current density of 1 μA/mm. The extracted interface trap density was 1 × 10 ¹² cm ^-2 · eV ^-1 at E _c - E _t = 0.442 eV, which resulted in negligible hysteresis and excellent dynamic characteristics.

This study investigated the effects of a thin aluminum oxynitride (AlO_xN_y) gate insulator on the electrical characteristics of AlGaN/GaN-on-SiC metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs). The fabricated AlGaN/GaN-on-SiC MIS-HEMTs exhibited a significant reduction in gate leakage and off-state drain currents in comparison with the conventional Schottky-gate HEMTs, thus enhancing the breakdown voltage. The effects of gate recess were also investigated while using recessed MIS-HEMT configuration. The Johnson’s figures of merit (= f_T × BV_gd) for the fabricated MIS-HEMTs were found to be in the range of 5.57 to 10.76 THz·V, which is the state-of-the-art values for GaN-based HEMTs without a field plate. Various characterization methods were used to investigate the quality of the MIS and the recessed MIS interface.

Turn-on voltage instability of beta-gallium oxide ( $\beta $ -Ga2O3) vertical trench Schottky barrier diodes (SBDs) with different fin-channel orientations was investigated. Fins oriented along the [010] direction exhibited the highest turn-on voltage stability and the smallest hysteresis, while fin channels oriented along the [100] direction exhibited the greatest instability. This study suggests that charge trapping at the sidewalls of $\beta $ -Ga2O3 trench SBDs differs based on the fin channel orientation and that fin channels oriented along the [010] direction possess the best electrical characteristics and reliability.

We have developed a low-temperature ohmic contact process with a recessed overhang configuration for Au-free (complementary metal-oxide semiconductor) CMOS-compatible AlGaN/GaN heterostructure field effect transistors (HFETs). The recessed overhang configuration has a Ti/Al bilayer directly in contact with the AlGaN/GaN heterojunction interface at the recessed sidewall overlaid with the AlGaN barrier layer, which allows good and reproducible ohmic formation with low-temperature annealing. The optimum Ti/Al thickness was 40/200 nm, which resulted in an R _c of 0.76 Ω mm with excellent surface morphology when annealed at 550 °C for 1 min. The device fabricated with a Ni/Mo gate exhibited a maximum drain current density of ∼500 mA mm ⁻¹ , a specific on-resistance of 1.35 m Ω cm ² and a breakdown voltage of >1 kV.