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 lambda m and exhibit stable surface-emitting electroluminescence even at a bending radius of}2 mm with exceptionally high luminance values of 595 and 175 cd/m(2) 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.