Wide-bandgap modification of polycrystalline ZnO using Sn component on the basis of developing quantum-well hetero-structure

We have grown semiconducting thin films—ZnO, SnO2 and their ternary compounds—using the Chemical Spray Pyrolysis (CSP) method. It was shown that the zinc–tin–oxide ternaries are most probably formed as Zn2(1−x)SnxO2. A remarkable increase in the bandgap energy is observed as the atomic fraction of Sn component, x, is increased. The bandgap-versus-x plot for the thin films is fitted to a quadratic formula with a bowing parameter of 0.76 eV. It was seen that the direct bandgap energy of the ternary films can be increased from 3.28 up to 3.45 eV at room temperature while x changes from 0.0 to 0.6, respectively. Such a change in bandgap energy is important for the establishment of the double-hetero- and superlattice structures and hence for the development of the quantum-well lasers. Moreover, the supposedly built barrier height between ZnO and Zn2(1−x)SnxO2 would be 85 meV, which is significantly higher than the room temperature thermal energy of 25 meV, so that this well will be quite adequate for electronic confinement even at higher device temperatures.