InGaN-based 405 nm near-ultraviolet light emitting diodes on pillar patterned sapphire substrates

Abstract

A study of GaN films and nitride based light emitting diodes (LEDs) grown on low density pillar structure (LDPS) and high density pillar structure (honeycomb like) sapphires patterned by chemical wet etching is described. Both types of patterned sapphire substrate (PSS) offered reduced defect density and improved performance of near-ultraviolet LED. In the case of LDPS patterned sapphire the correct choice of the pillar depth was found to be crucial for high quality crystal growth. A reduction of threading dislocation (TD) density from the level of 10⁸ cm⁻² down to the level of 2 × 10⁹ cm⁻² was observed. It was found that mostly enhanced light extraction rather than improved material quality caused the improvement of the LED performance.