Abstract
We fabricated three types of high luminous efficiency white light emitting diodes (LEDs). The first is the white LED, which had a high luminous efficiency (η~L~) of 161 lm/W with the high luminous flux (ϕ~v~) of 9.89 lm at a forwardbias current of 20 mA. The blue LED had a high power (ϕ~e~) of 42.2 mW and high external quantum efficiency (η~ex~) of 75.5%. The second is the high luminous efficiency white LED with a low voltage (V~f~) of 2.80 V, which was almost equal to the theoretical limit. η~L~ and wall‐plug efficiency (WPE) is 169 lm/W and 50.8%, respectively, at 20 mA. They are approximately twice higher than those of a tri‐phosphor fluorescent lamp (90 lm/W and 25%). The third is the high power white LED fabricated from the high power blue LED with high ϕ~e~ of 651 mW at 350 mA. ϕ~v~, η~L~ and WPE of the high power white LED are 145 lm, 134 lm/W and 39.6% at 350 mA, respectively. Moreover, at 1 A, ϕ~v~ and η~L~ were 361 lm and 97 lm/W, respectively. Thus ϕ~v~ is equivalent to that of a 30 W‐class incandescent lamp. And, η~L~ is slightly higher than that of a tri‐phosphor fluorescent lamp. Moreover, we fabricated the high power near ultra‐violet, bluish‐green and green LEDs, whose ϕ~e~ at 350 mA were 675 mA, 325 mW, and 236 mW, respectively. ϕ~v~ of the green LED was 128 lm at 350 mA. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)