This paper tries to explore the phosphor optical characteristics through reliability tests using white light emitting diodes (WLEDs) with a high color rendering index (CRI ,Ra¡Ö90). Based on light mixing principles and considering the high CRI, three color-coded powders were mixed separately with silicone into a phosphor, and then bottomed with blue chips into WLEDs. The three powders were oxide nitride (red), YAG (yellow), and silicate (green). Two kinds of samples were fabricated ¡V phosphor and emitters similar to commercial products. Both cool-white (CCT=5650~7000K, lumen efficiency¡Ö60 lum/w.) and warm-white (CCT=2850~3250K, lumen efficiency¡Ö50 lum/w.) samples passed the Bin Code distribution process and brightness measurement. The results indicate better lumen efficiency than previously published research. After the three kinds of mono-colored phosphors were created, .we implemented the reliability test in which three CREE standards were chosen. These standards were (1) high temperature with high humidity test (60¢J , 90% humidity) in operating and non-operating condition; (2) thermal shock test (-40¢J ~125¢J ); (3) life time test. The thermal shock test showed the decaying power of intensity for red, yellow, and green phosphors were 11.7%, 17.5%, and 19.3% respectively. These results demonstrate that the red phosphor has the best thermal resistance. However, after the high temperature with high humidity tests, the decaying power of intensity for red,yellow, and green phosphor were 15.7%, 10.1% and 6.4% correspondingly. These results show that the green phosphor has best aqua resistance. In the life time test of emitters, the decaying power of intensity for the cool-white emitter was 3.2%, while the warm-white emitter showed 4.2%. As such, cool-white emitters were concluded to have better reliability than warm-white emitters.

There are many intensive researches for zinc compounds due to their wide band gaps and potential applications in visible and UV optoelectronic technologies. Zinc nitride is a n-type semiconductor material having a direct band gap, and is not widely studied. Previous papers reported that zinc nitride is a n-type semiconductor having low resistivity and high electron mobility. Its band gap varies from 1.23 eV to 3.2 eV depending on the process condition. In this work, we successfully fabricated zinc nitride p-n junction by heat treatment on zinc nitride films. The threshold voltage of p-n junction is about 1 V. The Zinc nitride films were prepared by reactive RF magnetron sputtering. The as-grown zinc nitride thin film is a n-type material. It is found that the film treated at 300¢J for 3 hours can be changed to a p-type material. The zinc nitride has a very low resistance (2.2¡Ñ10-2 £[-cm) and high carrier concentration (3.88¡Ñ1019 cm-3) after the heat treatment. The optical band gap of zinc nitride was determined as a direct band gap varying from 1.1 eV to 1.6 eV according to the temperature of heat treatment. The zinc nitride was successfully prepared with various electrical characteristics and band gaps by controlling the temperature of heat treatment.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 95-100).

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Todd Weatherford, Ronald Pieper. Includes bibliographical references (p. 39-40). Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 158-170). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--School of Electrical and Computer Engineering, Georgia Institute of Technology, 2004. Directed by Nan M. Jokerst. / Vita. Includes bibliographical references (leaves 156-167).

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 207-219). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 107-119).

Thesis (M.S.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 2003. / Includes bibliographical references (p. 183-193).

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 75-77).