We present the first demonstration of RF characteristics of electrically injected GaN/InGaN core–shell nanowire-based micro light-emitting diodes (μLEDs) for μLED displays and visible-light communication. A record −3 dB modulation bandwidth ∼1.2 GHz at 1 kA/cm 2 (higher than any LED grown on c -plane GaN), and a low-leakage current–voltage characteristic with excellent rectifying behavior are achieved. Analysis using a small-signal equivalent electrical circuit for the μLEDs indicates a significantly longer differential recombination lifetime (∼330 ps) compared to the measured RC time constant (∼30 ps) at 1 kA/cm 2, confirming negligible effects from RC parasitic delay on the modulation speed. The bandwidth versus current density ( J ) characteristic shows a different trend compared to planar c -plane and m -plane reference μLEDs, even though the nanowires are composed of both polar c -plane and nonpolar m -plane sidewalls. The anomalous behavior of the bandwidth versus J characteristic is explained by nonuniform carrier injection, coupled with nonuniform quantum well thickness and indium composition, across the nanowire. The interpretation of the RF behavior of the nanowire-based μLEDs is supported by scanning transmission electron microscopy images, a significant blue shift (∼55 nm) of the electroluminescence spectra with applied bias, and nonuniform injection revealed by COMSOL simulations.
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Nami et al. (2019) studied this question.