Integration\nof InGaN/GaN Microrod Light Emitting Diodes\non Flexible and Peelable Substrate via Dielectrophoretic Alignments

Flexible GaN-based microlight emitting diodes (μ-LEDs)\nare\nmaking a significant impact in emerging wearable technology due to\ntheir excellent performance, characterized by smaller size, fast response,\nlow power consumption, and high luminance. However, most recent studies\nhave focused on the separation and alignment of individual μ-LEDs\non rigid substrates, rather than on flexible substrates. This study\nreports on the fabrication, separation, and horizontal alignment of\nrod-shaped InGaN/GaN μ-LEDs onto an interdigitated pattern using\nthe dielectrophoresis (DEP) technique on a flexible substrate. A low-surface-energy\npolytetrafluoroethylene layer is introduced beneath the flexible polyimide\nlayer, enabling physical peel-off from the rigid substrate. A maximum\nalignment efficiency of 82.3% is achieved on the flexible substrate\nvia conventional DEP with a sinusoidal electric field at 1 MHz. The\nfabricated flexible horizontally aligned μ-LED (FHAL) chip is\ntransferred onto carbon/copper tape for investigating optical and\nelectrical characteristics. The FHAL chip exhibits consistent brightness,\ncurrent–voltage, and electroluminescence characteristics even\nunder bending deformation states with a radius of curvature as small\nas 4.5 mm. The EL spectra of the FHAL chip show a lower full width\nat half-maximum of 23 nm when operated at 10 V, indicating superior\ncolor saturation compared to flexible ultrathin blue organic LEDs\n(50 nm). Furthermore, stable optoelectrical characteristics are observed\neven after repeated bending deformation tests up to 1000 times. This\nwork demonstrates that the proposed flexible, small pixel size, and\nhigh brightness FHAL chip is pertinent for emerging next-generation\nwearable display technology.