Filterless Discrimination of Wavelengths in the Range from Ultraviolet to Near-Infrared Light Using Two PdSe₂/Thin Si/PdSe₂ Heterojunction Photodetectors

Abstract

In this study, we present a wavelength sensor that is capable of distinguishing the spectrum in the range from ultraviolet (UV) to near-infrared (NIR) light. The filterless device is composed of two horizontally stacking PdSe2/20 μm Si/PdSe2 heterojunction photodetectors with a photovoltaic (PV) behavior, which makes it possible for the device to work at 0 bias voltage. Due to the relatively small thickness of Si and the wavelength-dependent absorption coefficient, the two PdSe2/20 μm Si/PdSe2 photodetectors according to theoretical simulation display a sharp contrast in distribution of the photoabsorption rate. As a result, the photocurrents of both photodetectors evolve in completely different ways with increasing wavelengths, leading to a monotonic decrease in the photocurrent ratio from 6800 to 22 when the wavelength gradually increases from 265 to 1050 nm. The corresponding relationship between both the photocurrent ratio and wavelength can be easily described by the monotonic function, which can help to precisely determine the wavelength in the range from 265 to 1050 nm, with an average relative error less than ±1.6%. It is also revealed that by slightly revising the monotonic function, the wavelength in other different temperatures can also be estimated.

A self-driven wideband wavelength sensor based on an individual PdTe2/Thin Si/PdTe2 heterojunction

“…40 According to our previous study, the width of the depletion region was only about 2 mm for the present device, while the diffusion length for the used n-Si with a carrier mobility of 500 cm 2 Vs À1 was about 316 mm, much longer than the thickness of thin Si of 20 mm. 23,42 Therefore, both the depletion and diffusion regions were within the entire thickness of the thin Si. As discussed above, short wavelength light was primarily absorbed in the superficial region of Si, whereas light with a long wavelength could be absorbed within the entire thickness of the thin Si.…”

“…Very recently, exploiting the wavelength-dependent optical absorption behavior, our group has proposed a new type of wavelength sensor, in which the photocurrents of two identical Schottky junctions or metal-semiconductor-metal (MSM) devices stacked parallelly have a sharply different evolution with varying light wavelength. [21][22][23][24] Thus, the curve of photocurrent ratio of two devices versus light wavelength follows a monotone function, giving the ability to discriminate light wavelengths in a broad spectrum range. Although these devices can accurately sense the broadband light wavelength with average absolute errors as low as several nanometers, the employment of two identical devices, however, inevitably brings about increased challenges in device fabrication and inconvenience in use.…”

Highly sensitive filterless near-infrared wavelength sensors with two self-driven MLG/Ge heterojunctions

“…All these demonstrate the high accuracy of the as-fabricated wavelength sensor in our work, which is comparable to the lately reported wavelength sensor in the visible range. 2,9,16,24,27 For a more complete description of the relationship between the photocurrent ratio and wavelength, a new fitting function is also achieved after taking into account the light intensity (see the ESI †). By using this function, the wavelength-dependent photocurrent ratio at various light intensities could be directly calculated.…”

“…Obviously, most of the current wavelength sensors are mainly used for UV light and visible light detection. 9,16,27,[36][37][38] But our devices have a near-infrared sensing region from 880 nm to 1650 nm, which may have great potential in the optoelectronic devices and systems of the near-infrared sensing area.…”

“…Lately, our group has developed several filterless wavelength sensors with two parallel devices, which could quantitatively determine the wavelengths ranging from 265 to 1050 nm through the relationship between the current ratio of the two devices and the wavelength. [25][26][27] Although the detector is optimized in terms of the device structure and function (good resolution in wavelength detection), its performance in the near-infrared range is still unsatisfactory. Inspired by this, we propose a new Ge-based wavelength sensor mainly concentrating on the near-infrared range.…”