Integration of high performance GaN LEDs for communication systems and smart society

In this work, we report on releasing GaN-on-Si LEDs from their original substrate and micro-transfer printing them into miniature reflective cavities with different depths to enhance the forward directed optical power. Results show that the 10 pm-deep cavities can redirect the light effectively, with the collected power increased by 80% compared to devices transferred on flat surface. With polymeric lenses deposited on the device in the cavity, the power is increased by a further 18% when compared to those without lenses. Combining all the steps, a total 9-times enhancement in collected light is achieved after transfer printing compared to LEDs on the original substrate. Finally, the capability of the printed LEDs in visible light communication is demonstrated. A higher signal-to-noise ratio and lower bit-error-rate is observed for printed LED into cavity compared with that of on flat target due to higher optical power. The strategy would be also useful for many other applications in miniaturized integration and colour conversion based displays.