Quantum dots excited InGaN/GaN phosphor-free white LEDs

Commercial GaN based white LEDs have been fabricated using phosphor coating of blue LEDs. We report on the growth of InGaN/GaN based white LEDs using In-rich InGaN quantum dots incorporated in the MQW layers. The photoluminescence spectrum of the MQWs shows a broad emission spectrum covering 400 to 700 nm. Cross-section TEM shows the existence of pyramidal shaped quantum-Re structures with size of 1.5-2.0 nm embedded in the InGaN well, To prevent the out-diffusion of these InGaN quantum dots in the well layer during thermal activation of p-GaN, a small amount of Indium was introduced into the p-GaN and the temperature was kept below 800 degrees C for p-InGaN epilayer growth. I-V measurement of the white LEDs gives a forward voltage of 5.2 V for a current of I-F similar to 20mA. The chromaticity coordinate ranges from 0.28 < x,y < 0.34 with a colour temperature of similar to 6000 K. The internal quantum efficiency was separately determined to be in excess of 50%.