Electrical characteristics of gallium nitride and silicon based metal-oxide-semiconductor (MOS) capacitors

The integration of high-kappa dielectrics with silicon and III-V semiconductors is important due to the need for high speed and high power electronic devices. The purpose of this research was to find the best conditions for fabricating high-kappa dielectrics (oxides) on GaN or Si. In particular, high-kappa oxides can sustain the high breakdown electric field of GaN and utilize the excellent properties of GaN.;This research developed an understanding of how process conditions impact the properties of high-kappa dielectric on Si and GaN. Thermal and plasma-assisted atomic layer deposition (ALD) was employed to deposit TiO2 on Si and Al2O3 on polar (c-plane) GaN at optimized temperatures of 200°C and 280°C respectively. The semiconductor surface treatment before ALD and the deposition temperature have a strong impact on the dielectric's electrical properties, surface morphology, stoichiometry, and impurity concentration. Of several etches considered, cleaning the GaN with a piranha etch produced Al2O3/GaN MOS capacitors with the best electrical characteristics. The benefits of growing a native oxide of GaN by dry thermal oxidation before depositing the high-kappa dielectric was also investigated; oxidizing at 850°C for 30 minutes resulted in the best dielectric-semiconductor interface quality. Interest in nonpolar ( m-plane) GaN (due to its lack of strong polarization field) motivated an investigation into the temperature behavior of Al2O3/ m-plane GaN MOS capacitors. Nonpolar GaN MOS capacitors exhibited a stable flatband voltage across the measured temperature range and demonstrated temperature-stable operation.