Identification of ZnO Defect Structure by PL Spectroscopy

Defect structure of ZnO determines the optoelectronic characteristics of ZnO crystal and film. The identification and modulation of the defect structure is the foundation of the manufacture of optoelectronic devices. Although a good deal of research has been carried out about intrinsic defects and doping defects in ZnO, it is difficult to obtain a conclusive result accepted by all. In the paper, ZnO film is prepared by sol-gel method and the defect structure is expressed by photoluminescent (PL) spectroscopy. Based on some basic rules the intrinsic defect structure of ZnO is confirmed and the interaction of impurity Li and intrinsic defect is discussed. At the same time, some new electronic levels are proposed. It is surprising that although there are fourteen peaks in PL spectra of ZnO film, almost all the peaks can be identified by these basic rules.

Photoluminescence of Cu(In1-X, GaX)Se2 Epitaxial Thin Films Grown by MOVPE

To study the intrinsic defect structure, detailed photoluminescence (PL) measurements of epitaxial Cu-rich Cu(In1-X, GaX)Se2 grown by metalorganic vapor phase epitaxy (MOVPE) were performed. Distinct emissions appear at an energy position 80-150meV below the bandgap. Excitation-power-dependent measurements showed blue shifts up to 18meV/decade for these emissions. The temperature dependent PL results in a defect energy for this emission of 50-80meV due to a free-to-bound (FB) transition. This indicates that the emissions of this material are controlled by fluctuating potentials due to high compensation or compositional inhomogeneity. The compositional inhomogeneity is detected by x-ray diffraction (XRD) and occurs especially for epitaxial layers grown at 570°C.