Step-Roughened N-face GaN Surface on InGaN Light-Emitting Diodes Using a Laser Decomposition Process

Abstract

InGaN-based light-emitting diodes (LEDs) with a step-inverted pyramidal structure at the GaN/patterned-sapphire interface were fabricated through laser decomposition and wet crystallographic etching processes. By partially reducing the GaN/patterned-sapphire contact area through the step-inverted pyramidal structure, the light output power of the treated LED structure was enhanced 21% compared to a conventional LED structure. By increasing the pulse operation current to 200mA (176 A/cm2), the related efficiency droop and the peak wavelength blueshift phenomenon of the electroluminescence spectrum were almost the same in both LED structures. The light emission intensity at the laser-treated stripe-line region, with the roughened N-face GaN surface, was higher than at the truncated triangle-shaped patterned-sapphire region. LEDs with step-inverted pyramidal structures and GaN/air-gap/patterned-sapphire structures increased light-extraction efficiency for high efficiency nitride-based LEDs.