Study of Ultranarrowband Silicon Nanowire Array Photodetector with Peak Spectral Responsivity at 1120 nm

Near-infrared (NIR) narrowband photodetectors, featuring high sensitivity, excellent wavelength selectivity, and narrow full width at half-maximum (fwhm), enable efficient detection of specific NIR wavelengths and are widely used in optical communication, environmental monitoring, spectroscopy, and scientific research. In this study, we present a self-powered NIR photodetector based on a silicon nanowire (SiNW) array, exhibiting an ultranarrowband response centered at 1120 nm. The device employs a simple Schottky junction architecture. The SiNW arrays were fabricated via metal-assisted chemical etching, with tunable nanowire diameters. Experimental results reveal that decreasing the nanowire diameter leads to a progressive narrowing of the fwhm and a redshift in the peak response wavelength. These changes are attributed to enhanced light-trapping and a charge collection narrowing (CCN) mechanism, which together improve wavelength selectivity and sensitivity. The core principle of CCN is adjusting the spectral dependence of charge collection efficiency, enabling the device to exhibit a high response only to specific optical wavelength ranges while suppressing others. The device with ∼50 nm diameter SiNW achieves a peak detectivity of 8.7 × 10¹¹ Jones at 1120 nm and an fwhm of only 83 nm. Under zero bias, the device exhibits a -3 dB bandwidth of 7.6 kHz, a linear dynamic range up to 106 dB, and ultrafast response speeds, with rise and fall times of 29 and 48 μs, respectively. These results highlight the strong potential of SiNW arrays in the development of high-performance narrowband photodetectors and offer a promising approach for future NIR optoelectronic applications.