Demonstration of high efficiency cascaded blue and green micro-light-emitting diodes with independent junction control
Panpan Li, Hongjian Li, Yifan Yao, Haojun Zhang, Cheyenne Lynsky, Kai Shek Qwah, James S. Speck, Shuji Nakamura, Steven P. DenBaars
Abstract
We demonstrate efficient cascaded blue/green micro-size light-emitting diodes (μLEDs) with independent junction control. The cascaded μLEDs, consisted of blue μLEDs, a tunnel junction, and green μLEDs, were fully grown by metalorganic chemical vapor deposition. Blue, green, and blue/green emissions can be independently controlled in the same device. The blue μLEDs (60 × 60 μm2) and green μLEDs (40 × 40 μm2) exhibit a forward voltage of 4.1 and 3.1 V at 20 A/cm2 and a high peak external quantum efficiency of 42% and 14%, respectively. This demonstration paves the way for monolithic integration of full color cascaded μLEDs.