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Abstract: We have investigated the electric-field intensity distributions and characteristics of the whispering-gallery mode (WGM) from a planar microdisk using a three-dimensional finite-difference time-domain method. Silicon nitride (Si3N4) planar microdisks on silica (SiO2) substrates have been systematically analyzed considering the effects of the sidewall angle, etching depth, and height. Superpositioning of the TE and TM modes which is caused by the skew effect according to the sidewall angle has been demonstrated. Furthermore, the mode splitting caused by the change from single mode to multi-mode regimes due to an increase in the height has been analyzed. Several planar microdisks of Si3N4 on SiO2 were fabricated, and their resonance characteristics were probed by using micro-photoluminescence spectroscopy. A quality factor of 5×103 for microdisks with a diameter of 3.5μm and sidewall angle of 35° was observed in the visible range. The WGMs of fabricated microdisk were analyzed according to the details of the model and found to be in good agreement [Copyright &y& Elsevier]

Abstract: Thermal annealing in NH3-ambient was carried out to form p-type ZnO films. The properties were examined by X-ray diffraction (XRD), Hall-effect measurement, photoluminescence (PL), and secondary ion mass spectrometry (SIMS). Electron concentrations in ZnO films were in the range of 1015–1017/cm3 with thermal annealing in NH3-ambient. The activation thermal annealing process was needed at 800 ∘C under N2-ambient to obtain p-type ZnO. The electrical properties of the p-type ZnO showed a hole concentration of 1.06×1016/cm3, a mobility of 15.8 cm2/V s, and a resistivity of 40.18 Ω cm. The N-doped ZnO films showed a strong photoluminescence peak at 3.306 eV at 13 K, which is closely related to neutral acceptor bound excitons of the p-type ZnO. The incorporation of nitrogen was confirmed in the SIMS spectra. [Copyright &y& Elsevier]

Abstract: The dependence of the MgO sputtering power on the structural and optical properties of epitaxially grown MgZnO thin films on GaN/sapphire substrates by radio-frequency magnetron sputtering was investigated. The photoluminescence investigation showed blue shift of 170 meV in MgZnO film grown at the MgO power of 300 W, compared with the ZnO films grown at the MgO power of 0 W, which was attributed to the enhancement of the Mg incorporation at higher power. In addition, increase in Mg mole fraction with increase in sputtering power of MgO was observed from the PL results, and a maximum of 6.6 at.% Mg was obtained at the MgO power of 300 W. The high-resolution X-ray diffraction and transmission electron microscopy (TEM) investigations revealed that the threading dislocation density in the MgZnO thin films increased with increase in sputtering power. Furthermore, microstructural analysis performed by TEM revealed formation of a thin cubic-like phase in the interface between GaN template and MgZnO thin film, together with increased thickness of the interfacial layer with sputtering power. [Copyright &y& Elsevier]