Improvement of vertical light extraction from GaN‐based LEDs on moth‐eye patterned sapphire substrates

A newly developed moth‐eye patterned sapphire substrate (MPSS) technology increased light extraction efficiency (LEE) in the vertical direction in nitride‐based blue light emitting diodes (LEDs). MPSS is characterized by a submicron‐scale periodical structure that exerts the Bragg diffraction effect at the interface between gallium nitride (GaN) and sapphire. Through simulations and experiments, it was revealed that emphasis of the diffraction effect by optimizing the MPSS structure enhanced vertical emission from LEDs. As a result, resin‐encapsulated, large‐sized LEDs on MPSS with a large diffraction effect achieved a high LEE of 0.76 that was comparable to that of commercially available thin‐film LEDs. Bird's‐eye view of scanning electron microscope (SEM) image of MPSS.