Oxygen mediated defect evolution in RF sputtered Ga2O3 thin films on p-Si substrate

Abstract

Impact of oxygen concentration in governing the structural and optical properties of RF sputter Ga 2 O 3 thin film deposited on p-Si at 500 o C by controlling the oxygen flow rate (OFR) has been demonstrated in this work. To maintain the oxygen rich and oxygen poor condition, the argon (Ar) to oxygen (O 2 ) ratio systematically varied from 1:1, 1:2, to 1:0, 2:1 and, 3:1 respectively. Such OFR reliant change in crystalline quality of the grown Ga 2 O 3 thin film is investigated by X-ray Diffraction (XRD) study. The atomic force microscopy results further illustrate an increase in film roughness owing to the inevitable introducing of defects/ oxygen vacancy ( V O ) during deposition with higher OFR. The modification in material stoichiometry via generation of V O and defects in surplus of oxygen is further supported with XPS analysis. Moreover, a rising trend of optical bandgap (Eg) due to transformation from oxygen rich to oxygen poor condition was revealed by spectroscopic ellipsometery study and further correlated with the improved crystallinity of the film. A maximum Eg of 4.44 eV was obtained for the Ga 2 O 3 thin film deposited with 3:1 Ar to O 2 ratio. Finally, the photoluminescence (PL) investigation confirms a strong correlation between defects/ V O generation with OFR variation. Where, the decrease in blue band contribution in lower oxygen concentration was correlated with reduced Vo concentration via its active participation in gallium vacancy V Ga and Vo pair (V Ga +Vo) formation. Finally, the impact of OFR on the Ga 2 O 3 /Si heterojunction device property is also investigated by utilizing the current–voltage (I-V) measurements, which shows a superior device performance for film grown in oxygen poor condition owing to the presence of lower defect concentration, surface roughness, and interface states. • Oxygen mediated structural, chemical and optical transformation of Ga 2 O 3 thin film deposited on p-Si substrate at 500 o C temperature by RF sputtering. • Impact of oxygen extremes on the defect evolution of Ga 2 O 3 thin film by photoluminescence study. • The heterojunction properties of β-Ga 2 O 3 /Si are studied electrically and such heterojunctions exhibit relatively superior rectification properties. • 3:1 is the optimum Ar to O 2 ratio to achieve high quality, defect-free Ga 2 O 3 film on Si.