Applied Physics Letters · 2020 · 184 citations · 23 references
EngineeringElectrical EngineeringMaterials ScienceOptoelectronicsSemiconductor DevicesSemiconductor MaterialsDevice CharacterizationLight-emitting DiodesSemiconductor Device MaterialsWide Band Gap SemiconductorsWide-bandgap Semiconductor DevicesWide-bandgap SemiconductorsAuger RecombinationChemical TreatmentExternal Quantum EfficiencyExtraction EfficiencyLight ExtractionLight Extraction EfficiencyLight-emitting DevicesQuantum Efficiency
Chemical etching and Al2O3 dielectric passivation were used to minimize nonradiative sidewall defects in InGaN/GaN microLEDs (mesa diameter = 2–100 μm), resulting in an increase in external quantum efficiency (EQE) as the LED size was decreased. Peak EQEs increased from 8%–10% to 12%–13.5% for mesa diameters from 100 μm to 2 μm, respectively, and no measurable leakage currents were seen in current density–voltage (J–V) characteristics. The position and shape of EQE curves for all devices were essentially identical, indicating size-independent ABC model (Shockley–Read–Hall, radiative, and Auger recombination) coefficients-behavior that is not typical of microLEDs as the size decreases. These trends can be explained by enhancement in light extraction efficiency (LEE), which is only observable when sidewall defects are minimized, for the smallest LED sizes. Detailed ray-tracing simulations substantiate the LEE enhancements.
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Absorption, Reflectance, and Luminescence of GaN Epitaxial Layers
R. Dingle, D. D. Sell, S. E. Stokowski et al. · Physical review. B, Solid state · 1971 · 526 citations