Photocarrier-Driven Passive Modulation for III-Nitride Optoelectronic System

This letter presents an investigation of passive modulation based on photogenerated carrier concentration variation in a suspended III-nitride multiple-quantum-well (MQW) optoelectronic system. The MQW structure exhibits an electroluminescence peak at 440 nm, and the on-chip platform integrates the transmitter, waveguide, modulator, and receiver in a monolithic configuration. These devices are designed and fabricated in a unified process using top-down etching and backside suspension techniques from a single silicon-based III-nitride wafer. The suspended microsystem is comprehensively characterized. Experimental results show that the passive modulation system maintains stable operation over a temperature range of -50 °C to 50 °C and continuous operation for 300 minutes. A modulation rate of up to 2 Mbps is achieved. This modulation scheme is distinguished by its independence from externally applied electric fields or driving currents, making it a promising candidate for ultra-low-power modulation in future III-nitride optoelectronic systems.