Near-Ultraviolet Nitride LEDs Grown on Pyramidal and Columnar Patterned Sapphire Substrates

摘要

Near-ultraviolet (UV) nitride-based light-emitting diodes (LEDs) have been fabricated on pyramidal (wet-etched) and columnar (dry-etched) patterned sapphire substrates (PPSs). The light output power (@20 mA) of the pyramidal PSS, columnar PSS and conventional InGaN LED samples (λ_D=403 nm) show 8.82, 7.85 and 6.88 mW, respectively. A 25% enhancement in output power can be achieved in the pyramidal PSS LED as compared with that of the conventional LED sample. This could be due to a combination of improved light extraction efficiency and the reduction in dislocation density using a pyramidal PSS. The wet-etched pyramidal reflector array in the PSS could provide more probability of escaping photons from the GaN/sapphire interface, which agreed well with the ray-tracing simulation results on both pyramidal and columnar PSS LED samples.