Bandgap Engineering of ZnO Transparent Conducting Films

Low resistivity and transparent Al doped ZnMgO films were deposited on glass substrates by a pulsed laser deposition system. For up to 32 atm% of Mg content, segregation of a MgO phase was not observed. The bandgap of these films could be widened to about 4 eV with increasing Mg content. The relation between bandgap and resistivity was found to be a trade-off; i.e. the larger the bandgap, the higher the resistivity. The maximum bandgap among films with an electrical resistivity of less than 10-3 Ω cm was 3.94 eV. The average optical transmittance of these films was more than 90 % for wavelengths λ between 400 and 1100 nm. The transmittance around λ = 330 nm was still 50 %.