All-GaN monolithic self-monitoring HEMT-μLED-PDs

We demonstrate the monolithic integration of high-electron-mobility transistors (HEMTs), micro-light-emitting diode (μLED) pixels, and photodiodes (PDs) on a single GaN platform. The integrated HEMTs enable precise voltage-controlled dimming operation of μLED pixels under both direct current (DC) and pulse-width modulation (PWM) schemes, with the latter exhibiting spectral stability essential for micro-displays. Crucially, the adjacent PDs can function as in-situ, pixel-level optical sensors within an ultra-compact footprint, providing not only real-time photocurrent response under both DC and PWM operation but also a qualitative calculation of the light intensity for μLED pixels under PWM dimming. The established self-monitoring architecture eliminates the requirement of external sensors and complex optics, representing a practical solution for high-uniformity all-GaN monolithic micro-displays with built-in brightness monitoring and calibration capability.