Papers by Keyword: Optical Emission

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Authors: D.H. Kang, Jae Chul Song, Dong Wook Kim, J.S. Kim, Kannappan Santhakumar, Cheul Ro Lee
Abstract: We report the microstructure and optical properties of gallium nitride (GaN) epilayers grown on lens shape patterned sapphire substrate (PSS) using metalorganic chemical vapor deposition (MOCVD) for various growth times. A lens shaped pattern was used to reduce the threading dislocation density and to improve optical emission efficiency. A scanning electron microscope (SEM) image shows flat and smooth surface of GaN grown on PSS at 80 min which could be achieved by lateral growth from the trench region. From the DCXRD spectra, full width at half maximun (FWHM) value was decreased with increasing growth time. FWHM of the sample grown at 80 min was 473.5 arc sec. This indicates there is an improvement in crystalline quality of the GaN grown on PSS as the growth time increases. From photoluminescence (PL) spectra, an increase in band edge emission intensity and a decrease in defect related yellow luminescence was observed for GaN on PSS as the growth time increased. From the PL spectra, FWHM was 82.2 meV at peak position 363.9 nm for the sample grown for 80 min. It is clearly seen that the threading dislocations can be reduced by lateral growth improving the light emission efficiency by internal light reflection on the lens surface for GaN grown on PSS.
Authors: D. Sarkar, J.M. Calleja, H.P. van der Meulen, J.M. Becker, R.J. Haug, Klaus Pierz
Authors: A.P. Marchetti, M.I. Freedhoff, D. Rodney, G.L. McLendon
Authors: Yang Jiao
Abstract: Plasma emission spectroscopy was used to study the evolution behavior of the Zn ions in the plasma produced by nanosecond pulsed laser beam irradiating on pure zinc metal targets. The measurements indicated that the hotter and denser region in the plasma was located at about 0.75mm from target surface and presented at delay time 250 ns with respect to the laser pulse. Compared to Zn atoms in the plasma expansion, the results reveal that Zn ions are characterized by weaker intensity in spatial profiles and shorter lifetime in temporal evolution, while, much higher brightness of Zn ions can been observed in early-state plasma emission.
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