White-Light Emission From GaN-Based TJ LEDs Coated With Red Phosphor

Abstract

We report the fabrication of white light-emitting diode (LED) lamps by coating red phosphor onto the green/blue dual-color tunnel-junction (TJ) LED chips. For the dual-color TJ LED chips without phosphor coating, it was found that electroluminescence intensity of the green peak increased faster than that of the blue peak, as we increased the injection current. Under the same injection current, it was found that power consumption and heat generation were larger for the TJ LEDs, as compared with the conventional blue LED chips. By coating 0.1-g red phosphor onto the $660 \times 760~\mu \text{m}^{2}$ dual-color TJ LED chips, we achieved white LED lamps with color temperature, $T_{C}$ , of 4102 K, color-rending index, CRI, of 68, and the Commission Internationale de L’Eclairage color coordinates of (0.32, 0.36). Furthermore, it was found that $T_{C}$ observed from the dual-color TJ LED + red phosphor white LED lamps were smaller than those observed from the blue LED+yellow phosphor white LED lamps.