Electrically Injected InGaN/GaN micro-Light Emitting Diodes: Size-dependent diode characteristics and recombination dynamics

This work demonstrates InGaN/GaN multiple quantum well (MQW) micro-light emitting diodes (µLEDs) grown on c-plane sapphire substrates via metalorganic chemical vapor deposition, focusing on size-dependent efficiency, leakage, and temperature-dependent performance. Micro-LEDs with radii of 1-50 µm were fabricated using nanofabrication techniques. Current-voltage characteristics, modeled using a two-diode approach, reveal that peripheral leakage decreases with radius, and ideality factors indicate near-ideal behavior for larger devices. Electroluminescence measurements reveal a high slope efficiency for smaller radii at low bias, accompanied by early compression in devices with radii of 1-2.5 µm, attributed to the high carrier density. The ABC recombination model quantifies Shockley-Read-Hall, radiative, and Auger processes, showing size-dependent nonradiative contributions. Electroluminescence spectra exhibit a blueshift with bias, attributed to the quantum-confined Stark effect (QCSE) screening, which is pronounced in smaller devices. Temperature-dependent electroluminescence exhibits non-monotonic intensity, striking a balance between radiative efficiency gains and hole freeze-out in p-GaN. These findings highlight the interplay of QCSE, leakage, and carrier dynamics, advancing efficient µLEDs.