Improvement of the Emission Intensity of GaN-Based Micro-Light Emitting Diodes by a Suspended Structure

Herein, suspended GaN-based micro-light emitting diodes (LEDs) are ingeniously proposed and fabricated, showing a substantially enhanced light emission compared to conventional micro-LEDs on the sapphire substrate. The suspended architecture is prepared by transferring epitaxial layers to micrometal pillars on the copper plate after removing the original sapphire substrate. The photoluminescence intensity of the suspended micro-LED exhibits 150% higher than that of the normal device, and the electroluminescence intensity is increased by 114% in the current injection range of 0-10 mA. The enhancement of the output intensity benefits from the partially relaxed strain of the epitaxial film and the resultant reduction of the quantum confined Stark effect in the InGaN quantum well active region, as well as the improved light extraction efficiency due to the larger light-escaping area and less optical absorption and trapping, which are unambiguously verified by Raman spectroscopy and ray-tracing simulations. This study provides a new promising route to design and fabricate highly efficient micro-LEDs for practical applications.