Flexible InGaN LEDs on a Polyimide Substrate Fabricated Using a Simple Direct-Transfer Method

An array of InGaN-based flexible light-emitting diodes (FLEDs) was fabricated on a full-scale 2-in polyimide substrate. An InGaN epitaxial layer on a sapphire substrate was directly bonded with a polyimide substrate, and the sapphire substrate was then removed via a laser lift-off process. A subsequent n-GaN etching process for a chip isolation finished LED chips over the entire 2-in polyimide substrate. Using this simple direct-transfer process, we obtained a production yield of over 97%. The FLED device operated linearly up to an input current level of 500 mA. Output power, operating voltage, and wavelength shift of the FLED up to 400-mA driving current were nearly the same as for a vertical LED on metal substrate.