Al2O3 has been an attractive gate dielectric for GaN power devices owing to its large conduction band offset with GaN (~2.13eV), relatively high dielectric constant (~9.0) and high breakdown electric field (~10 MV/cm). Due to exceptional control over film uniformity and deposition rate, atomic layer deposition (ALD) has been widely used for Al2O3 deposition. The major obstacle to ALD Al2O3 on GaN is its high interface-state density (Dit) caused by incomplete chemical bonds, native oxide layer and impurities at the Al2O3/GaN interface. Therefore, an appropriate surface pretreatment prior to deposition is essential for obtaining high-quality interface. In this study, we investigated the effect of TMA, H2O and Ar/N2 plasma pretreatment on Dit and border traps (Nbt). 5 cycles of TMA purge, 5 cycles of H2O purge and Ar/N2 plasma pretreatment were conducted on GaN prior to deposition of ALD Al2O3. Al2O3/GaN metaloxide-semiconductor capacitors (MOSCAPs) were fabricated for the characterization of Dit and Nbt using UV-assisted capacitance-voltage (C-V) technique. The results show that TMA and H2O pretreatment had trivial effects on interface engineering whereas Ar/N2 plasma pretreatment slightly reduced Dit and significantly reduced Nbt.
We report the use of sol-gel method at room ambient to grow nanoscale thin film of Ga2O3 on Si surface for both surface
passivation and gate dielectric. The admittance measurements were carried out in the frequency range of 20 kHz-1 MHz
at room temperature. Voltage dependent profile of interfacial trap density (Dit) was obtained by using low and high
frequency capacitance method. The capacitance (C)-voltage (V) analyses show that the structures have a low interfacial
trap density (Dit) of 1x1012 cm-2eV-1. The Ga2O3 thin film synthesized via sol-gel method directly on devices to function
as a gate dielectric film is found to be very effective. We also present our experimental results for a number of gate
dielectric and device passivation applications.