Gallium oxide (Ga2O3) is a promising wide bandgap semiconductor for power electronic applications. Investigation into the conduction mechanism of Ga2O3 Schottky diodes is important for improving the device performance. In this study, the forward-biased temperature dependent current-voltage (I-V-T) characteristics of Ni/(-201) β-Ga2O3 Schottky diodes have been investigated in the temperature range of 298-473 K. The apparent barrier height (ϕ_ap) increased while the ideality factor (n) decreased with the increase in temperature. Such a temperature dependent behavior of ϕ_ap and n was explained by the inhomogeneity of ϕ_ap, which obeyed Gaussian distribution with mean barrier height of 1.8 eV and standard deviation of 201 mV. Subsequently, zero-bias barrier height (¯ϕ_B0) and Richardson constant (A*) were obtained from the slope and intercept of the modified Richardson plot as 1.18 e V and 94.04 A·cm-2·K-2, respectively. The ¯ϕ_B0 obtained from the modified Richardson plot was in good agreement with the theoretical value calculated from the work function of Ni and electron affinity of β-Ga2O3. The I-V-T characteristics of Ni/-Ga2O3 Schottky diodes can be successfully explained by the thermionic emission theory with a single Gaussian distribution of the barrier height.
Al<sub>2</sub>O<sub>3</sub> 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 Al<sub>2</sub>O<sub>3</sub> deposition. The major obstacle to ALD Al<sub>2</sub>O<sub>3</sub> 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, H<sub>2</sub>O and Ar/N<sub>2 </sub>plasma pretreatment on D<sub>it</sub> and border traps (N<sub>bt</sub>). 5 cycles of TMA purge, 5 cycles of H<sub>2</sub>O purge and Ar/N<sub>2</sub> plasma pretreatment were conducted on GaN prior to deposition of ALD Al<sub>2</sub>O<sub>3</sub>. Al<sub>2</sub>O<sub>3</sub>/GaN metaloxide-semiconductor capacitors (MOSCAPs) were fabricated for the characterization of D<sub>it</sub> and N<sub>bt</sub> using UV-assisted capacitance-voltage (C-V) technique. The results show that TMA and H<sub>2</sub>O pretreatment had trivial effects on interface engineering whereas Ar/N<sub>2</sub> plasma pretreatment slightly reduced D<sup>it</sup> and significantly reduced N<sub>bt</sub>.
We report the use of sol-gel method at room ambient to grow nanoscale thin film of Ga<sub>2</sub>O<sub>3</sub> 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 (D<sub>it</sub>) 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 (D<sub>it</sub>) of 1x10<sup>12</sup> cm<sup>-2</sup>eV<sup>-1</sup>. The Ga<sub>2</sub>O<sub>3</sub> 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.