Processing and characterization of monolithic passive-matrix GaN-based microLED arrays with pixel sizes from 5 to 50 µm

MicroLED arrays with the capability of switching each pixel separately with high frequency can serve as structured micro-illumination light engines for applications in sensing, optogenetics, microscopy and many others. We describe a scalable chip process chain for the fabrication of passive-matrix microLED arrays, which were integrated with PCB-based driving electronics. The arrays were produced by deep-etching of conventional planar LED structures on sapphire, followed by filling and planarization steps. The pixel resolution lies in the range of 254 to 2540 pixels-per-inch (ppi), the arrays consist of 32 x 32 pixels. Optical output powers up to 50 μW per pixel were measured. In comparison to CMOS-based approaches, the presented technology is a simplified strategy to producemicroLED arrays with high pixel counts.