Study on Light Extraction from GaN-based Green Light-Emitting Diodes Using Anodic Aluminum Oxide Pattern and Nanoimprint Lithography

An anodic aluminum oxide (AAO) patterned sapphire substrate, with the lattice constant of 520 ± 40 nm, pore dimension of 375 ± 50 nm, and height of 450 ± 25 nm was firstly used as a nanoimprint lithography (NIL) stamp and imprinted onto the surface of the green light-emitting diode (LED). A significant light extraction efficiency (LEE) was improved by 116% in comparison to that of the planar LED. A uniform broad protrusion in the central area and some sharp lobes were also obtained in the angular resolution photoluminescence (ARPL) for the AAO patterned LED. The mechanism of the enhancement was correlated to the fluctuations of the lattice constant and domain orientation of the AAO-pattern, which enabled the extraction of more guided modes from the LED device.