MOCVD Growth of Thick β-(Al)GaO Films with Fast Growth Rates

In this work, we investigated the epitaxial growth of (010) β-Ga 2 O 3 and β-(Al x Ga 1– x ) 2 O 3 films using metalorganic chemical vapor deposition (MOCVD) with trimethylgallium (TMGa) as the precursor, aiming for high growth rates for thick films. We observed pyramid-shaped defects in the β-Ga 2 O 3 epitaxial films, characterized by polygon-shaped bumps and inverted pyramids embedded in the epi-films. To improve the surface morphology and suppress the defects formation, we developed a novel approach that incorporates a small amount of aluminum (Al) during the growth process. This addition led to significant improvements in surface morphology and reductions in both the density and size of defects for the low-Al β-(Al x Ga 1– x ) 2 O 3 films, with a growth rate of 5.5 μm/h. Our findings demonstrate the effectiveness of this approach in optimizing the surface morphology of thick β-(Al x Ga 1– x ) 2 O 3 films with rapid growth rates. We achieved the best surface for β-(Al x Ga 1– x ) 2 O 3 in an 11 μm-thick film with approximately 2% Al composition, grown at a rate of 5.5 μm/h. However, we also observed that defect density and size increase with film thickness. Room temperature Hall measurements were used to characterize the electrical properties of the low-Al β-(Al x Ga 1– x ) 2 O 3 films, which revealed a decrease in Si incorporation efficiency and room temperature mobility with increasing Al composition. Results indicated that increasing the chamber pressure led to a decrease in both growth rate and Al composition at a constant [TMAl]/[TMGa + TMAl] molar flow rate ratio. The β-(Al x Ga 1– x ) 2 O 3 films (∼11 μm) with optimal surface quality were grown at chamber pressures between 60 and 100 torr. This work demonstrates the feasibility of growing (010) low-Al β-(Al x Ga 1– x ) 2 O 3 thick films with high growth rates and minimal surface defects using MOCVD. Our findings provide valuable insights into β-(Al)GaO growth and suggest that introducing Al is an effective strategy for improving the surface morphology of β-(Al)GaO films. These results have important implications for the development of high-performance (Al)GaO-based vertical power devices.