Estimation of Band Gap Energy of Mgx Zn1‐xO Films by Photocurrent

The band gap energy (E-g) of high-quality Mg-x Zn1-xO films grown on ZnO (0001) substrates by the plasma-assisted reactive evaporation method using a ZnMg alloy could be estimated by the photocurrent (I-ph). Measurement of Iph was more useful than photoluminescence (PL), transmittance or reflectance (R) spectra measurements for determination of E-g of materials with large binding energy of the excitons. The values estimated from the relation of (akh?)2hv plots using optical absorption coefficient ak calculated from extinction coefficient k were close to the peak energy of PL or R of these films. The values estimated from the relation of (aphhv)(2)h gamma plots using inter-band absorption coefficient aph calculated from Iph spectra were larger than the values of peak energy of PL or R despite strong absorption of the excitons. Therefore, it was thought that these values are closer to Eg. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)