Using Different Methods to Measure the Optical Energy Bandgap of Un-annealed and Annealed Ga₂O₃ Films

In this study, electron beam (E-beam) was used to deposit Ga₂O₃ films on the sapphire (Al₂O₃) substratest, then Ga₂O₃ films were divided three groups, unannealed, annealed at 850 °C, and annealed at 950 °C, respectively. After that, three different methods were investigated to find the optical energy bandgap of un-annealed and annealed Ga₂O₃ films. First was used n&k analyzer to measure all the optical energy bandgaps of un-annealed and annealed Ga₂O₃ films directly; Second, all the measured transmittance spectra of un-annealed and annealed Ga₂O₃ films, then the cut wavelength at the zero transmittance ratio of the extrapolated straight line according the slope of the absorption edge was used to measure optical energy bandgap using the equation of Eg= 12400/cut wavelength. Third, the curve of (αhν)² against the energy (hν) value was plotted according to Eqs. αhν = C (hν – Eg)^1/2 and T = (1 – R)² exp(-αd), and the extrapolated straight line was used to measure the optical energy bandgap of un-annealed or annealed Ga₂O₃ films. Finally, the measured results were well compared.