Characterization of flexible InGaN LEDs with various curvatures

• We investigated the properties of flexible InGaN LEDs with various curvatures R.
• The output power of the LEDs slightly increased as R decreased.
• The output power decreased at currents larger than a critical current.
• This critical current was smaller for devices with a smaller R.
• The compressive strain and the piezoelectric field increased as R decreased.

We investigated the properties of flexible InGaN LEDs fabricated on a 2-in. polyimide substrate with various radii of curvature R. The output power of the LEDs slightly increased as R decreased for a given input current. The output power decreased and surface cracks appeared in the curved devices at currents larger than a critical current, although this current was smaller for devices with a smaller R. Reverse-biased electro-reflectance spectroscopy revealed that both the compressive strain in the InGaN layers and the related piezoelectric field increased as R decreased.