Integration of InGaN/GaN Microrod Light Emitting Diodes on Flexible and Peelable Substrate via Dielectrophoretic Alignments

Abstract

Flexible GaN-based microlight emitting diodes (μ-LEDs) are making a significant impact in emerging wearable technology due to their excellent performance, characterized by smaller size, fast response, low power consumption, and high luminance. However, most recent studies have focused on the separation and alignment of individual μ-LEDs on rigid substrates, rather than on flexible substrates. This study reports on the fabrication, separation, and horizontal alignment of rod-shaped InGaN/GaN μ-LEDs onto an interdigitated pattern using the dielectrophoresis (DEP) technique on a flexible substrate. A low-surface-energy polytetrafluoroethylene layer is introduced beneath the flexible polyimide layer, enabling physical peel-off from the rigid substrate. A maximum alignment efficiency of 82.3% is achieved on the flexible substrate via conventional DEP with a sinusoidal electric field at 1 MHz. The fabricated flexible horizontally aligned μ-LED (FHAL) chip is transferred onto carbon/copper tape for investigating optical and electrical characteristics. The FHAL chip exhibits consistent brightness, current–voltage, and electroluminescence characteristics even under bending deformation states with a radius of curvature as small as 4.5 mm. The EL spectra of the FHAL chip show a lower full width at half-maximum of 23 nm when operated at 10 V, indicating superior color saturation compared to flexible ultrathin blue organic LEDs (50 nm). Furthermore, stable optoelectrical characteristics are observed even after repeated bending deformation tests up to 1000 times. This work demonstrates that the proposed flexible, small pixel size, and high brightness FHAL chip is pertinent for emerging next-generation wearable display technology.