Bandwidth enhancement in hexagonal M-plane InGaN/GaN MQW micro-photodetectors via TMAH sidewall treatment

We report on the bandwidth enhancement of InGaN/GaN multiple quantum well (MQW) micro-photodetectors (micro-PDs) via tetramethylammonium hydroxide (TMAH) sidewall treatment. M-plane hexagonal micro-PDs were fabricated, where anisotropic TMAH wet etching was employed to eliminate plasma-induced sidewall damage and suppress leakage current. Capacitance–voltage (C–V) measurements confirm that the treatment effectively reduces sidewall parasitic capacitance, thereby minimizing the RC delay in miniaturized devices. Additionally, eye diagram test results indicate a significant improvement in signal-to-noise ratio following sidewall repair. Consequently, a 10-μm micro-PD achieved a −3 dB bandwidth of 1.79 GHz at a reverse bias of 70 V under 450 nm laser illumination, alongside a peak responsivity of 46 mA/W. Furthermore, the micro-PD exhibits outstanding thermal stability up to 100 °C. These results indicate the potential of GaN MQW-based micro-PDs for high-speed chip-to-chip optical interconnects.