Effect of the shape of nanometer-scaled patterns on sapphire substrate on the efficiency of light emitting diode

In this study, a 2 inch sized a highly periodic nanometer-scaled patterned sapphire substrate (NPSS) was fabricated using nanoimprint lithography (NIL) and inductively coupled plasma etching to improve the light-extraction efficiency of GaN-based lightemitting diodes (LEDs). Both truncated cone and cone shape patterns were fabricated on the sapphire substrate to compare the enhancement effect of light extraction efficiency of LEDs according to the shape of sapphire patterns. A blue LED structure was grown on the two different NPSS, and the photoluminescence (PL) and electroluminescence (EL) were measured to confirm the effectiveness of the two different nanometer-scaled patterns on sapphire. An improvement in luminescence efficiency was observed when NPSS was applied; 2 times stronger PL intensity and 2 times stronger EL intensity than the LED structure grown on the un-patterned sapphire substrate was measured. These results show highly periodic nanometer-scaled patterns create multi-photon scattering and effectively enhance the light-extraction efficiency of LEDs.