Characteristics and luminescence of Ge doped ZnO films prepared by alternate radio frequency magnetron sputtering

Ge doped ZnO films have been deposited on Si(1 0 0) substrates by alternate rf sputtering of ZnO and Ge. The effects of doping and annealing on the optical and structural properties have been investigated by means of X-ray diffraction and photoluminescence (PL) spectra. With the increasing annealing temperature, the intensity of the ZnO(0 0 2) diffraction peak increases, indicating that the crystalline quality of the film improves. The samples annealed at 800 and 1000 8C there appear the GeO and GeO2 diffraction peaks, and the intensity of the near ultra-violet emission at 395 nm increases greatly, while a weak yellow emission appears at 590 nm. The near ultra-violet emission could be attributed to the GeO color centers and exciton recombination. The yellow peak is probably related to Ge incorporated in the ZnO structure.