Tauc-plot scale and extrapolation effect on bandgap estimation from UV-vis-NIR data - A case study of beta-Ga2O3

The effect of the Tauc plot scale and bandgap extrapolation technique on estimated optical bandgap values is often not strongly emphasized. Herein, we demonstrate that the scale of the conventional Tauc plot and the extrapolation technique poses significant influence on the determined value of bandgap. The nanomaterial used for this study was prepared by the CVD method using different H-2 reducing gas flow rates. XRD measurements confirmed polycrystalline beta-Ga2O3 with high crystalline quality. FE-SEM analysis revealed nanohump-like morphology. UV-vis-NIR measurements generally showed increasing bandgap with rising H-2 supply into the horizontal reactor. Specifically, it was observed that the proper extrapolation technique for bandgap estimation is more appropriate as compared to the values obtained from the traditional direct extrapolation method. It is established that direct extrapolation technique has the potential to either under - or over-estimate bandgap values, whereas the proper extrapolation method is promising for more reasonable values of optical energy gap.