Phosphor-free InGaN nanopillar white LEDs by random clustering of mono-sized nanospheres

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.

This work was supported by the General Research Funds of the Research Grant Council of Hong Kong (Nos. 17204218 and 17205318). The computations were performed using research computing facilities offered by HKU Information Technology Services.