Band gap modulation of ZnTe_(1-x)O_x alloy film by control of oxygen gas flow rate during reactive magnetron sputtering

摘要

The band gap energy of ZnTe_(1-x)O_x alloy films grown on c-plane sapphire substrates was modulated by controlling the argon-oxygen ratio during radio frequency magnetron sputtering. The ZnTe_(1-x)O_x samples were deposited at a substrate temperature of 200 °C and with gas mixtures of 2%-8% oxygen in argon. The optical transparency of the ZnTe_(1-x)O_x samples was measured in the 1.5-6.0 eV energy range by optical transmission spectra. The optical band gap, obtained from plots of (αhν)~2 as a function of hν, increased from 2.2 to 4.9 eV with increasing oxygen ratio, believed to be a result of a change in bonding structure through composition exchange during film deposition by reactive magnetron sputtering. These results show that the band gap energy of ZnTe_(1-x)O_x, ZnOTeO, and (ZnO)_(1-x)(TeO_2)_x alloy films can be modulated, making them more suited for applications as windows and as active layers for ZnTe-based intermediate band solar cells.