Interface engineering in epitaxial growth of sputtered β-Ga2O3 films on Si substrates via TiN (111) buffer layer for Schottky barrier diodes

The native amorphous silicon oxide (SiO2) layer formed on the Si substrate leads to the (100) preferred orientation for β-phase gallium oxide (β-Ga2O3), which encounters various defects in β-Ga2O3, such as twin boundaries and stacking faults etc. The (111) preferred orientation of titanium nitride (TiN) hetero-buffer layer can be used in the interface between β-Ga2O3 and Si substrates to reduce the lattice mismatch between them and increase the (˗201) preferred orientation for β-Ga2O3. The lattice mismatch between TiN (111) and β-Ga2O3 (˗201) is 0.76%, which is less than the β-Ga2O3 (˗201)/Si (111) about ˗6.3%. The β-Ga2O3 and TiN films were grown using radio-frequency magnetron sputtering on Si substrates, which possess polycrystalline nature as revealed using X-ray diffraction patterns and high-resolution transmission electron micrographs. The optimal parameters are found as, process atmosphere: Ar = 10 sccm, RTA: 800 °C for β-Ga2O3/TiN (300 nm)/Si. This work highlights the effect of the TiN hetero-buffer layer, the process atmosphere, and annealing temperatures on the microstructural and surface morphology of β-Ga2O3 films. The lateral Schottky barrier diode (SBD) were fabricated using the optimized β-Ga2O3/TiN (300 nm)/Si film. The Baliga's Figure of Merit (BFOM) of the lateral SBD is 7.60 × 10−2 kW/cm2, which exhibits 4 order of BFOM higher than that of β-Ga2O3/Si SBD due to interface engineering. The β-Ga2O3/TiN (300 nm)/Si hetero-structure demonstrates a promising material to be employed in the next generation β-Ga2O3 based power devices.