A study on structural formation and optical property of wide band-gap Be_(0.2)Zn_(0.8)O layers grown by RF magnetron co-sputtering system

摘要

Wide band-gap BeZnO layers were grown on Al_2O_3 (0001) substrate using radio-frequency magnetron co-sputtering. The rate of Be_xZn_(1-x)O crystallized as a hexagonal structure was x=0.2. From the X-ray photoelectron spectroscopy measurement, the O-Zn bonds relating the crystal structure and the Be-O bonds related to the deviation of the stoichiometry in the BeZnO layer were caught at 530.4 and 531.7 eV in the 0 1s spectrum, respectively. Thus, the observance on the Be Is peak of 113.2eV associated with the bonding Be-O indicates that the sputtered Be atoms are substituted for the host-lattice site in ZnO. This Be-O bonding shows a relatively low intense and broadening spectrum caused by large fluctuation of Be content in the BeZnO layer. From the photoluminescence and transmittance measurement, the free exciton and the neutral donor-bound exciton (D~0, X) emissions were observed at 3.7692 and 3.7313 eV, respectively, and an average transmittance rate over 95% was achieved in a wide ultraviolet (UV)-visible region. Also, the binding energy for the (D~0, X) emission was extracted to be 37.9 meV. Through the wide band-gap material BeZnO, we may open some possibilities for fabricating a ZnO-based UV light-emitting diode to be utilized as a barrier layer comprised of the ZnO/BeZnO quantum well structure and/or an UV light emitting material itself.