Photoluminescence enhancement of GaN-based LEDs structure with nano-grayscale multiple quantum wells using electron beam lithography

Abstract

Photoluminescence (PL) enhancement is achieved by using a novel nano-grayscale (NGS) InGaN/GaN multiple quantum wells (MQWs) structures. NGS patterns on the n-GaN layer were fabricated with a low contrast electron beam resist by electron beam lithography and inductively coupled plasma dry etching process. The periods of NGS patterns on the n-GaN layer are 100 and 200nm. NGS InGaN/GaN MQWs structure on the n-GaN layer was realized by subsequent epitaxial growth with metalorganic vapor phase epitaxy (MOVPE). Photoluminescence studies reveal that the LEDs with NGS InGaN/GaN MQWs structures show up to 28.5% enhancement of luminescence intensity compared to the sample with conventional flat MQWs structure. In addition, the PL emission peak shows a blue shift from 452 (flat MQWs) to 446nm (NGS sample with a 200nm period), which may be explained by a partial strain release in MQWs that induces a lower piezoelectric field in the active layer.