Inspection of micro-LED dies by using liquid crystal films

The development of micro-LED technology has progressed to small sizes of just a few microns and has attracted great interest for display applications. However, inspecting small-sized micro-LED dies using traditional electroluminescence methods poses challenges. This work demonstrates a novel, to the best of our knowledge, method for inspecting micro-LED dies by placing a liquid crystal (LC) film over the micro-LED wafer. When illuminated, micro-LED dies can generate an open-circuit voltage through the photovoltaic effect, which can be detected by observing changes in the transmittance of the LC film. The proposed approach shows that voltages of several volts can be effectively detected using LC films.