Monolithic Integration of GaN-Based Flexible Microcantilever for Opto-Electromechanical Force Sensing

This study presents a novel micro-opto-electromechanical coupling force sensor realized on a monolithic GaN-on-Si process platform. Unlike commercial optical sensors that require significant space and additional fiber, the proposed device monolithically integrates a micro light-emitting diode (micro-LED) on a GaN-based microcantilever with a photodetector (PD) on a single chip, thereby achieving light emission, transmission, and reception. Experimental results show that a$100-\mu \mathrm{A}$current was applied to the micro-LED, the PD photocurrent increased from 5.8 to 7.5 nA under different probing strokes, corresponding to a sensitivity of$0.04 \text{nA} / \mu \mathrm{m}$. These results confirm that the proposed monolithic integration method enables a high-precision, compact opto-electro-mechanical force sensor by improving coupling efficiency and reducing assembly complexity.