Research of compact bright UV lamp using nitride semiconductor nano-phosphor and cold cathode

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We researched deep-UV lamp which light originates from GaN nanostructures. The size of prepared GaN nano-phosphor is 200 nm in diameter. From transmission electron microscopy (TEM) observation, the nano-phospor is single crystal, and has no dislocations, which means that crystal quality is very high. The GaN nano-phosphor showed strong band-edge luminescence. The good optical properties resulted from high crystal quality of GaN nanocrystals. To shorten the emitted wavelength, AlGaN nano-phosphors were prepared. With increasing the Al content, emitted wavelength was shifted shorter region to 346 nm.As materials for cold cathode of the UV lamp, GaN nanowires and carbon nanotubes (CNT) were grown. GaN nanowires were grown by vapor-solid-liquid growth mode. The diameter and length of the GaN nanowires were 20 nm and over 5μm, respectively. Field electron emission from GaN nanowires was measured. The electron emission was observed and the turn-on field was 13 V/μm. As the growth method of CNT, we established a new CNT growth method which the formation of catalytic nano-particles and the growth of CNT were carried continuously in an identical growth chamber. Both the catalytic nano-particles and CNT were grown by thermal chemical vapor deposition. The growth of multi-walled CNT was found by TEM observation. Field emission properties of the CNT were measured. Threshold field and current density were 9 V/μm and > 100 μA/cm^2, respectively. These are good results which imply a possibility of CNT electron emitter for the UV lamp.We made a prototype of UV lamp consisting of the GaN nano-phospor and cold cathode. We obtained UV emission from the lamp. The UV lamp has a monochromatic spectrum, which a peak centered at 366 nm corresponding to the energy gap of GaN.