MicroLED technology faces challenges such as achieving higher brightness for outdoor use, improved efficiency for portable devices, and higher resolution for augmented reality/virtual reality (AR/VR) applications. Meeting these demands requires the miniaturization of light-emitting diodes (LEDs) to micrometer scales. Indium gallium nitride/gallium nitride (InGaN/GaN) nanowire heterostructures are promising due to their high luminescence efficiency and tunable emission wavelength, but miniaturization introduces defects that negatively impact efficiency. This thesis investigates indium gallium nitride/gallium nitride (InGaN/GaN) quantum wells grown via plasma-assisted molecular beam epitaxy (PA-MBE) on gallium nitride (GaN) pillars fabricated using metal-organic vapor phase epitaxy (MOVPE). While the nanowire morphology facilitates strain relaxation and In incorporation, point and extended defects, which act as non-radiative recombination centers, remain significant challenges. To suppress point defects generated in the GaN pillars grown at high temperatures by MOVPE and improve the luminescence efficiency of nanowire heterostructures, an InGaN under-layer (UL) is inserted prior to the growth of the InGaN active region. However, the incorporation of intrinsic and/or extrinsic point defects may still occur during the growth of the active region by PA-MBE. To better understand the variations in cathodoluminescence (CL) intensity attributed to point defects, a statistical methodology analyzing the CL intensity of hundreds of nanowires emitting at different wavelengths has been developed. The number of point defects incorporated during the growth of the active region is quantitatively determined, assuming that point defect incorporation is randomly distributed and follows Poisson statistics. Statistical methods reveal that while point defect incorporation generally follows Poisson statistics, deviations arise due to extended defects such as threading dislocations and stacking faults leading to partial dislocations observed via high-resolution scanning transmission electron microscopy (STEM), supported by Geometrical Phase Analysis (GPA). These findings highlight the validity of the methodology of using CL mapping based on Poisson’s statistics, in quantifying point defects within a large ensemble of nanowires.

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Contact : Bruno Daudin​