Optical characteristics of Ge doped ZnO compound

The compound of ZnO: Ge which can be used as a blue light emission material has been prepared by the solid state reaction method. We have discussed the optical properties of the compound by photoluminescence (PL) measurements. We discovered that Zn2GeO4 phase is formed by the heavy doping of Ge atoms, and the solid solubility limit of Ge in ZnO is about 0.7 mol%. From the observed PL spectra of the compound there is a blue shift up to 0.7 mol%, but in concentrations higher than 0.7 mol% a red shift is observed. We can explain the shift of PL peak by Burstein-Moss and the band tail effects.