Influence of HCl concentration in source solution and growth temperature on formation of α-Ga₂O₃ film via mist-CVD process

Abstract We have examined the effect of synthesis conditions on α -Ga 2 O 3 film, one of the ultra-wide bandgap semiconductors, on c -plane sapphire substrate via mist CVD process. The resultant film is dominantly composed of α -Ga 2 O 3 phase, but a small amount of κ -Ga 2 O 3 phase coexists when the growth temperature is higher. The source solution containing higher concentration of HCl expands the range of temperatures at which single-phase α -Ga 2 O 3 is grown and suppresses the inclusion of κ -Ga 2 O 3 at higher growth temperatures. Moreover, the growth with higher concentration of HCl up to 0.66 mol l −1 increases the growth rate and improves the surface roughness. Thus, HCl has a crucial role in the selective growth of α -Ga 2 O 3 and the quality of the film. Also, some pits are observed at the surface of α -Ga 2 O 3 and κ -Ga 2 O 3 is precipitated inside the pit defect when the concentration of HCl is low and the growth temperature is high.