Optical Characterization of Zn1-xCdxO Alloys Grown by Molecular-Beam Epitaxy

Abstract

We have carried out comprehensive optical studies to evaluate structural and bandgap properties of Zn1-xCdxO alloys with x {less than or equal to} 0.17 grown by molecular beam epitaxy. High crystalline quality of the alloys was concluded from cathodoluminescence measurements. Based on absorption and reflectance measurements, the compositional dependence of the bandgap energy of ZnCdO, estimated without taking into account excitonic effects, was found to follow the trend Eg(x)=3.28- 2.23x+0.45x2. Degradation in the alloy quality due to possible phase separation was found to cause deviations from this trend, evident from a more rapid red shift of the absorption edge. Effects of Cd incorporation on the variation of the bandgap energies with temperature are also discussed.