A Stepped Silicon-based Detector for Broad-Wavelength Detection from 365 to 1170 nm

Abstract

Wavelength discrimination is typically achieved by conventional multispectral approaches that rely on complex optics or multi-material filters, which incur high costs and limit miniaturization. Here, we propose a stepped silicon-based wavelength sensor that leverages silicon's intrinsic wavelength-dependent absorption for spectral discrimination. The device features two symmetric Au/Si/Au photodetectors deposited on defined steps of a 500 µm n-type silicon substrate. This vertical separation creates distinct optical paths when the upper detector is illuminated, causing shorter wavelengths to generate carriers near the surface while allowing longer wavelengths to penetrate deeper for absorption by the lower detector, thereby yielding complementary spectral responses. The photocurrent ratio between the two photodetectors exhibits a monotonic relationship with incident wavelength, enabling filter-free wavelength determination over a wide spectral range (365–1170 nm). In the specific near-infrared range of 1010–1170 nm, the relative error in wavelength detection is confined to ±0.3%.