Nanoimprinted patterned sapphire with silica array for efficient InGaN-based green mini-LEDs.

Here, we propose nanoimprinted patterned sapphire with a silica array (PSSA) with the aim to promote the efficiency of InGaN-based green (∼520 nm) mini-LEDs. According to x-ray diffraction measurements, the threading dislocation density of GaN epitaxial layers grown on nanoimprinted PSSA demonstrates a pronounced reduction compared with the epilayers on the conventional patterned sapphire substrate (PSS). Consequently, a mini-LED on PSSA exhibits a significantly boosted light output power (LOP) in comparison to a mini-LED on PSS. At 10 mA, the LOP of the mini-LED on PSS is 6.0 mW, and this is further improved to 6.8 mW for the mini-LED on PSSA. Moreover, the peak external quantum efficiencies of the mini-LEDs on PSS and PSSA are 41% and 47%, respectively. A three-dimensional (3D) finite-difference time-domain simulation demonstrates that the PSSA contributes enhanced light extraction for photons emitted from the active region. It is also highly feasible to use this nanoimprinted PSSA technology in red and blue mini-LEDs for the realization of full-color displays.