High-quality oxide/nitride/oxide gate insulator for GaN MIS structures

We report on a SiO2/Si3N4/SiO2(ONO) gate insulator stack deposited on GaN by jet vapor deposition (JVD) technique. Capacitors fabricated using the JVD-ONO on GaN are characterized from room temperature to 450 degreesC using capacitance-voltage (C-V), current-voltage (I-V), ac-conductance, and constant-current stress measurements. We find excellent operating characteristics over the measured range, most notably: 1) very low leakage current, 2) extremely high hard-breakdown strength, 3) low interface-trap density, and d) low net dielectric-charge density. Moreover, these performance figures remain well within acceptable limits even for operating temperatures as high as 450 degreesC. In addition, we measure both the capture cross-section of the interface traps and the surface-potential fluctuation at the GaN/ONO interface. All results suggest that JVD-ONO is an excellent choice for a gate dielectric in GaN-based MISFETs.