Phosphor-free InGaN nanopillar white LEDs by random clustering of mono-sized nanospheres
Wai Yuen Fu, H. W. Choi
Abstract
Nanosphere lithography with mono-sized nanospheres has been employed as a patterning tool of nanostructuring to achieve phosphor-free white-light emission in this study. Nanostructuring of InGaN/GaN quantum wells induces spectral blue shift due to strain relaxation, the extent of which depends on the sizes of the nanopillars. Nano-clusters of various sizes are formed as a result of random clustering of the mono-sized nanospheres, so that the clusters emit at different wavelengths as they are strain-relaxed to different levels. A Monte Carlo simulation has been employed to simulate the clustering patterns, while molecular dynamics and k·p Schrödinger calculations have been carried out to identify the appropriate nano-cluster distribution for phosphor-free white-light emission. The fabricated device achieves a color rendering index (CRI) of about 76 with an overall luminous efficacy of 2.6 lm/W under DC operation and 11.0 lm/W under pulsed operation.