Abstract
White light output was realized through combining a cerium-doped yttrium
aluminum garnet (YAG:${\hbox{Ce}}^{3+}$) phosphor with a gallium nitride (GaN)-based blue light-emitting
diode (LED). In order to coat a phosphor layer of high quality on a GaN chip,
the slurry coating technique was applied and investigated because of the coating
efficiency and uniformity. The phosphor layer of conformal structure was realized
on the LED chip with the self-exposure method. The influences of ammonium
dichromate (ADC) as photosensitizer of photoresist in the slurry are discussed.
Two methods are brought forward to reduce the absorption of Cr ions introduced
by ADC. And experimental results indicate that these two methods are feasible
to increase the luminous efficiency of white LEDs.
© 2009 IEEE
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