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 oC, and annealed at 950 oC, 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.