AlGaN-based deep-UV LEDs fabricated on connected-pillar AlN buffer

Abstract

260 nm-band AlGaN deep-ultraviolet (DUV) light-emitting diodes (LED) was fabricated on a connected-pillar AlN buffer layer grown on a sapphire substrate. Low threading dislocation density (TDD) connected-pillar AlN buffer is considered to be quite effective for obtaining high internal quantum efficiency (IQE) and light-extraction efficiency (LEE) in DUV-LEDs. We fabricated an AlN pillar array structure with accurate hexagonal shape pillars grown on a patterned sapphire substrate (PSS) by using an NH3 pulsed flow multi-layer (ML) growth and an epitaxial lateral overgrowth (ELO). The AlN pillars were connected to be flat surface AlN buffer layer with low TDD, through ELO process. We fabricated AlGaN quantum well (QW) DUV-LED on a connected-pillar AlN buffer. The output power obtained was 5.5 mW for 265 nm LED measured under room temperature cw operation.