AlGaN-based deep-ultraviolet self-monitoring micro-LED arrays

Monolithic integration of micro-light emitting diodes (μLEDs) arrays, waveguide, and photodiodes (PD) was achieved on 275 nm deep-ultraviolet (DUV) LED epitaxial wafers, enabling in-situ self-monitoring μLED arrays. It revealed significant size-dependent effects on the electrical and optical characteristics of μLEDs. Arrays with mesa diameters of 220 μm, 140 μm, and 60 μm exhibited enhanced current spreading, where the 60-μm devices achieved peak external quantum efficiency (EQE) of 4.19%, optical power density of 5.65 W/cm², and maximum light output power (LOP) of 45 mW per integrated chip. During 60 μm μLED arrays operation, the integrated self-driven PD achieved a photocurrent-to-dark-current ratio (PDCR) of 10⁶. Finally, ray-tracing simulations verified the distinct advantages of TM and TE mode photons in waveguide transverse propagation and light extraction, respectively. The compact monolithic DUV μLED chip demonstrated stable operation at high current densities, enabling it as a promising light source for OWC systems.