High efficiency GaN-based LEDs and lasers on SiC

Group III-nitride layers have been grown via metal-organic vapor-phase epitaxy (MOVPE) on single crystal-silicon carbide (SiC) substrates and fabricated into light-emitting diodes (LEDs) and laser diodes (LDs). Deep ultraviolet (UV) LEDs from 321 to 343 nm operating at 20 mA and 4.1 V exhibit an output of 0.2-2.9 mW, respectively, corresponding to an external quantum efficiency (EQE) of 0.26-4.0%. In the visible spectrum, an EQE of similar to47% was achieved in the blue at 455-460 nm corresponding to an output of 25.5 mW at 20 mA and 3.1 V. The value of EQE decreased to similar to30% at 395nm (violet) and similar to22% at 535nm (green). Interaction between defects and charge carriers is speculated to dominate the radiative recombination process at shorter wavelengths (< similar to440 nm) whereas evidence is presented that piezoelectric polarization dominates at longer wavelengths, predominantly in the green. White LEDs have been fabricated using 24 mW blue chips via phosphor excitation and exhibit luminous efficacies of 78 lumens/W, which is considerably more efficient than standard incandescent bulbs. Continuous-wave (CW) LD operation from 348-410 nm, and pulsed operation as short as 343 nm were achieved. (C) 2004 Published by Elsevier B.V.