Study of Far‐Field Electroluminescence Emission to Enhance Micro‐LED Performance

This study investigates the angular dependence of far‐field electroluminescence (EL) emission in InGaN/GaN LEDs and micro‐LEDs to enhance their performance for micro‐display and visible optical communication applications. We developed a measurement setup to analyze far‐field EL emission across various wavelengths and compared the results with 1D optical simulations. This approach allowed us to observe the well‐known dependence of emission directivity and light extraction efficiency (LEE) on the structural parameters of flip‐chip LEDs, particularly the thicknesses of p‐GaN and n‐GaN layers, and to quantify the impact of total thickness variation resulting from wafer thinning processes. Using larger LEDs, the test vehicle offers a valuable tool for designing micro‐LEDs with the desired directivity and for process monitoring. We also observed that the angular dependence of far‐field emission varies with the applied bias and demonstrated how this could affect wafer‐level micro‐LED characterizations. Finally, we showed that the far‐field EL emission of micro‐LEDs progressively deviates from the description by a 1D optical cavity alone, suggesting an increasing influence of the limited size and necessitating 3D‐FDTD simulations to accurately model both vertical cavity and sidewall effects. However, for sizes down to 5 μm, the directivity predicted by a 1D model seems roughly preserved.