Ultra-low-light visible–near-infrared position-sensitive detector based on femtosecond laser nitrogen-hyperdoped silicon

We introduce position-sensitive detectors (PSDs) based on femtosecond laser-structured sulfur-doped, nitrogen-doped, and S-N co-hyperdoped black silicon. In contrast to crystalline silicon, black silicon-based PSDs exhibit linear lateral photovoltage dependent on the light spot position. Thermal annealing at 873 K induces a tenfold enhancement in the position sensitivity of nitrogen-doped black silicon, reaching 129 mV/mm under white light irradiation. The device exhibits spectral response to 460-1150 nm wavelengths, achieving 99.7 mV/mm sensitivity with < 7% nonlinearity at 1000 nm under a low light power of 0.22 mW. These results demonstrate the potential of 873 K-annealed nitrogen-doped black silicon for self-powered, broadband PSDs with large sensitivity, high linearity, and ultra-low-light detection capability.