Distinguishing Wavelength Using Two Horizontally Stacking Graphene/Thin Si/Graphene Heterojunctions

In this work, we have developed a wavelength sensor that is capable of distinguishing illumination with wavelengths ranging from ultraviolet (UV) to near infrared (NIR). The as-proposed wavelength sensor is geometrically composed of two parallelly stacking graphene (Gr)/thin Si/Gr heterojunction devices, which are identical in device structures, but can display completely different optical properties in terms of distribution of photo-absorption and photo-generation rates under various light illuminations, according to theoretical simulation. Such a discrepancy in optical properties due to a wavelength dependent absorption coefficient and the relatively thin Si wafer gives rise to completely different photocurrent evolution for varied wavelengths of illumination. The relationship between the photocurrent ratio of devices, the wavelength and intensity of incident light can be numerically described by an equation, through which the wavelength in the range from 265 to 1050 nm can be accurately determined. Notably, the average root-mean-square error of this wavelength sensor is about 2.30 nm, with a relative error as low as ±1.5%, which is much better than other wavelength detectors previously reported. These results suggest that the present wavelength sensor may find potential application for future optoelectronic systems.