Temperature dependent electroluminescence of high performance InGaN/GaN nanorod light emitting diode arrays fabricated by nanosphere lithography and chemical mechanical polishing processes
| Autor: | Ying-Yuan Huang, 黃英原 |
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| Rok vydání: | 2010 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 98 Due to the superior optical and electrical characteristics, GaN and related materials attract great interests as the new short wavelength lighting source. However, GaN based nanostructures still have some limitations, such as the lack of low cost nanostructure processes and the difficulties of parallel metal evaporation on tips of nanorods without short circuit. In order to achieve GaN based nanorod structures, some groups used nickel nanomasks or ITO grown by oblique-angle deposition to approach. However, they still suffer from large leakage current and low efficiency. In this thesis, we demonstrated a novel practical approach to fabricate a p-i-n nanorod light emitting diode (LED) arrays using nanosphere lithography for nanorod formation, PECVD (plasma enhanced chemical vapor deposition) grown SiO2 layer for sidewall passivation, and chemical mechanical polishing for uniform nanorod contact. Our nano-device demonstrates a reverse leakage current 4.77nA at -5V, an ideality factor 7.35, and an optical output intensity 6807mW/cm2 at the injection current density 32A/cm2 (20mA). Comparing with results shown by other groups, our work shows the best output power and the least reverse leakage current among relative researches. It showed that our methods have great industrial applicability for low-cost manufacturing high efficient GaN-based LEDs. Furthermore, we demonstrated the nanorod structures can mitigate quantum confined Stark effect, and improve the internal quantum efficiency. We compared the temperature and current dependent electroluminescence (EL) of blue planar and nanorod LEDs over a wide temperature range. We found that the photon energy of nanorod LEDs as the current level increased at room temperature are nearly constant. It reveals that our nanorod structures can effectively mitigate the strain induced quantum confined Stark effect, enlarge the overlap of electron and hole wavefunctions, and then effectively improve the internal quantum efficiency of GaN light emitting diodes. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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