Toward Wide-Angle III-Nitride Miniaturized LEDs: Device Engineering and Photon Extraction Strategy

Abstract

Miniaturized LEDs (mini-LEDs) constitute a high-quality light source in the backlight unit (BLU) of liquid crystal displays (LCDs). However, the Lambertian light field distribution of mini-LEDs leads to limited viewing angles and decreased uniformity in BLU. Here, a high-performance wide-angle mini-LED is demonstrated via device engineering and an innovative photon extraction strategy. By integrating distributed Bragg reflectors (DBRs) on the light emission surface of mini-LED, propagation behaviors of photons are manipulated and thus altered Lambertian light field distribution into heart-shaped light field distribution, realizing the construction of wide-angle mini-LED. Furthermore, the effects of the reflectivity of various DBRs on the light field distribution and optoelectronic characteristics of wide-angle mini-LEDs are systematically investigated. To boost the external quantum efficiency (EQE) of wide-angle mini-LEDs, a photon extraction strategy, including optimizing sapphire substrate thickness and employing multiple laser stealth scribing techniques is proposed. As a result, the optimal wide-angle mini-LED exhibits a peak light intensity angle of 38°, a full width at half maximum of angular light intensity distribution of 162° and a 21.3% increment in peak EQE, in comparison to the wide-angle mini-LED without utilizing photon extraction strategy. It believes these innovations provide a substantial advancement in developing wide-angle mini-LEDs, contributing to their application in LCDs.