Fully Flexible GaN Light‐Emitting Diodes through Nanovoid‐Mediated Transfer

Recently, achieving flexible and highly efficient light‐emitting elements is the most noticeable demand for lighting or displays. Here, fully flexible gallium nitride (GaN) light‐emitting diodes (LEDs) are demonstrated based on a unique transfer method. The LED structure consisting of GaN pyramid arrays are first fabricated on an amorphous glass‐based template with a low‐temperature gallium nitride/titanium (LT‐GaN/Ti) hetero‐interface, then released and embedded into a flexible or stretchable substrate using a specialized interface control. Nanovoids created during thermal annealing render the hetero‐interface weaker than the other interfaces. This interface is further weakened by a post‐mechanical treatment for gentle release of the GaN pyramid arrays from the interface during a transfer process. The LEDs typically have a total thickness of }70 lm and exhibit stable surface‐emitting electroluminescence even at a bending radius of }2 mm with exceptionally high luminance values of 595 and 175 cd/m2 at peak wavelengths of 514 and 483 nm, respectively. The results suggest a route to high brightness, large, flexible/stretchable blue or green lighting or displays. Fully flexible GaN‐LEDs yielding bright green or blue light are demonstrated. The LED structure, consisting of hard GaN light‐emitting arrays embedded in a soft polymer matrix, is advantageous for high flexibility. This is enabled by accurately reducing the adhesion strength of the LT‐GaN/Ti hetero‐interface and transferring the stack arrays into ultrathin, flexible substrates.