A study on structural formation and optical property of wide band-gap Be0.2Zn0.8O layers grown by RF magnetron co-sputtering system

Wide band-gap BeZnO layers were grown on Al2O3 (0 0 0 1) substrate using radio-frequency magnetron co-sputtering. The rate of BexZn1−xO 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 O 1s spectrum, respectively. Thus, the observance on the Be 1s peak of 113.2 eV 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 (D0, 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 (D0, 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.