Heterogeneous Integration of Microscale GaN Light-Emitting Diodes and Their Electrical, Optical, and Thermal Characteristics on Flexible Substrates

Materials and device strategies to form inorganic, thin-film, microscale light-emitting diodes (micro-LEDs) are presented based on a simplified release method. High performance gallium nitride based blue micro-LEDs are fabricated on and released from both patterned sapphire substrates (PSSs) and conventional nonpatterned sapphire substrates (CSSs). Micro-LEDs are transferred onto copper and polyimide based flexible substrates and their electrical and optical performances are maintained. Thermal properties of PSS and CSS based micro-LEDs are systematically explored on different substrates. Finally, micro-LEDs combined with phosphor coatings demonstrate capability for polychromatic emission. The techniques presented here provide promising paths to advanced light sources with potential applications in lighting, displays, and biomedicine.