The enhancement of light-emitting efficiency using GaN-based multiple quantum well light-emitting diodes with nanopillar arrays

摘要

The quest for higher modulation speed and lower energy consumption has inevitably promoted the rapid development of semiconductor-based solid lighting devices in recent years.GaN-based light-emitting diodes (LEDs) have emerged as promising candidates for achieving high efficiency and high intensity,and have received increasing attention among many researchers in this field.In this paper,we use a self-assembled array-patterned mask to fabricate InGaN/GaN multiquantum well (MQW) LEDs with the intention of enhancing the light-emitting efficiency.By utilizing inductively coupled plasma etching with a self-assembled Ni cluster as the mask,nanopillar arrays are formed on the surface of the InGaN/GaN MQWs.We then observe the structure of the nanopillars and find that the V-defects on the surface of the conventional structure and the negative effects of threading dislocation are effectively reduced.Simultaneously,we make a comparison of the photoluminescence (PL) spectrum between the conventional structure and the nanopillar arrays,achieved under an experimental set-up with an excitation wavelength of 325 mm.The analysis demonstrates that MQW-LEDs with nanopillar arrays achieve a PL intensity 2.7 times that of conventional LEDs.In response to the PL spectrum,some reasons are proposed for the enhancement in the light-emitting efficiency as follows:1) the improvement in crystal quality,namely the reduction in V-defects; 2) the roughened surface effect on the expansion of the critical angle and the attenuated total reflection; and 3) the enhancement of the light-extraction efficiency due to forward scattering by surface plasmon polariton modes in Ni particles deposited above the p-type GaN layer at the top of the nanopillars.