Electrically Injected GHz-Class GaN/InGaN Core–ShellNanowire-Based μLEDs: Carrier Dynamics and Nanoscale Homogeneity

We present the first demonstration of RF characteristics of electrically injected GaN/InGaN core shell nanowire-based micro light-emitting diodes (mu LEDs) for mu LED displays and visible-light communication. A record -3 dB modulation bandwidth similar to 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 mu LEDs indicates a significantly longer differential recombination lifetime (similar to 330 ps) compared to the measured RC time constant (similar to 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 mu LEDs, even though the nanowires are composed of both polar c-plane and nonpolar m-plane sidewalls. The anomalous behavior of bandwidth versus J characteristic is explained by the 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 mu LEDs is supported by scanning transmission electron microscopy images, a significant blue shift (similar to 55 nm) of the electroluminescence spectra with applied bias, and nonuniform injection revealed by COMSOL simulations.