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We utilize a rate equation approach and RF measurement technique to study carrier dynamics in InGaN/GaN LEDs. Study of carrier dynamics aids in understanding efficiency challenges and design of high-speed, efficient micro-LEDs for visible-light communication and micro-LED display applications.

III-nitride high-speed optoelectronics are emerging for a variety of applications, including visible-light communication (VLC) in light-fidelity (Li-Fi) networks, optical communication using photonic-integrated circuits, and micro-pixel LED displays. III-nitride materials offer efficient light emission and the potential to route, modulate, and detect light on a single chip. Previous research into III-nitride optoelectronics has mainly focused on developing emitters with high efficiencies and large optical output powers, which are needed for conventional lighting and data storage applications. Here, we present the more recent development of III-nitride high-speed emitters, including planar micro-LEDs, nanowire-based micro-LEDs, and superluminescent diodes. We demonstrate record-high modulation bandwidths by growing devices on nonpolar and semipolar orientations of GaN, which are free from the polarization-related effects that limit the modulation bandwidths of $c$ -plane III-nitride. We also combine a rate equation model with an RF measurement technique to extract the carrier dynamics in the devices [1].

We report the fabrication and electro-optic characterization of nonpolar GaN-based superluminescent diodes with a tapered waveguide design. The devices were grown and fabricated on freestanding m-plane GaN. An electrical −3dB modulation bandwidth of 2.5 GHz is reported at the highest current density.

We demonstrate a high-speed nonpolar InGaN/GaN micro-LED with a record −3dB bandwidth of 1.5 GHz at a current density of 1 kA/cm2. The high-speed at low current density is attributed to the large electron-hole wavefunction overlap in nonpolar QWs leading to a shorter carrier lifetime.

Ultra-low resistance ohmic contacts on n-GaSb with specific transfer resistances down to 0.12 Ω-mm and specific contact resistances of ~1.1e-6 Ω-cm2 have been successfully fabricated on semi-insulating (SI) GaAs substrates using the Interfacial Misfit Dislocation (IMF) technique. The IMF technique enables epitaxial growth of GaSb layers on semi-insulating GaAs substrates resulting in vertical current confinement not possible on unintentionally ~ 1e17 cm-3 p-doped bulk GaSb. Results for low resistance ohmic contacts using NiGeAu, PdGeAu, GeAuNi and GeAuPd metallizations for various temperatures are reported. The low annealing temperature of NiGeAu and PdGeAu metallizations show promising results, but the lifetime of a device with these contacts have not yet been studied.