Enhancement in light extraction efficiency from GaN based LEDs with nanopores ITO p-contact grown on patterned sapphire substrate

摘要

Blue light emitting diodes (LEDs) have been fabricated with InGaN/GaN well layers (QWs) on micro-patterned sapphire substrate (PSS). Low pressure growth of GaN layer on PSS effectively reduces the density of edge dislocations. The growth of InGaN/GaN MQWs on PSS as compared to conventional sapphire substrate (CSS) improves the internal quantum efficiency (IQE) from 50 to 56%. The higher thermal barrier for luminescence thermal quenching ensures of more e–h pair recombination at the quantum wells and improves the IQE. The light extraction efficiency (hextr) from the LEDs is enhanced with use of PSS substrate and nanopores generation on the ITO p-contact. This would be attributed to the improvement in the quality of GaN film through reduction of threading dislocations and scattering of light from the sidewalls of the patterned sapphire.