Biaxial stress-dependent optical band gap, crystalline, and electronic structure in wurtzite ZnO: experimental and ab initio study

The relationship between band gap and biaxial stress in wurtzite ZnO thin films is examined by side-inclination x-ray diffraction technique and optical absorbance spectrum as well as ab initio calculation. The difference between ZnO and GaN is because of the large valence-band maximum (VBM) offset of ZnO to low energy and the strong p-d coupling in valence band of ZnO is responsible for the large VBM offset.