Bias-Selectable Dual-Mode SOI/PbSe Heterojunction for Visible-to-Shortwave Infrared Photodetector

Silicon-integrated broadband photodetectors covering a wide spectral range are important for next-generation optoelectronic systems. Directly building heterojunctions based on the stacking of bulk silicon and narrow-bandgap semiconductor thin films has emerged as an interesting research focus, considering their simple and effective fabrication methods. However, the long diffusion length of the charge carriers limits the response time, and the intrinsic lack of gain of the photodiode results in low infrared response in devices. In this work, we report a bias-selectable broadband and high photography-responsive Si/PbSe heterojunction photodetector fabricated on silicon-on-insulator (SOI) substrate. Specifically, the device operates in photodiode mode under reverse bias with responsivities of 4 mA/W and 3 μA/W at 520 and 1550 nm, respectively. Under forward bias, the device is in photoconductor mode with responsivities of 6 A/W and 250 mA/W at 520 and 1550 nm, respectively. Additionally, the response times of the device are 450/390 ns and 7/8 μs under reverse and forward bias, respectively. Our results may provide solutions for the future development of miniaturized and multifunctional Si-integrated infrared detectors for broadband imaging and miniaturized spectrometers.