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

Abstract

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 (η extr ) 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.