Ultra-Compact Wideband Microdisk SI-GE Avalanche Photodetector

We design and fabricate an ultra-compact wideband Si-Ge avalanche photodetector (APD) based on a microdisk resonator incorporated with a lateral PN junction. The device has a radius as small as 3.70 μm and it is fabricated using a standard foundry multi-project wafer (MPW) run, which facilitates cost-effective volume fabrication. The fabricated APD exhibits a low breakdown voltage of -5.66 V, leading to low power consumption in avalanche mode. At a bias voltage of -5.75 V, slightly lower than the breakdown voltage, the APD achieves a high responsivity of 8.50 A/W at -30 dBm input power and a wide bandwidth of 19.20 GHz. The proposed APD holds key advantages of ultra-compact footprint, low operating voltage, high responsivity, and wide bandwidth, making it promising for large-scale optical interconnection networks and microwave photonic systems.