A Complete Two-Dimensional Avalanche Photodiode Based on MoTe2−WS2−MoTe2 Heterojunctions With Ultralow Dark Current

Abstract

Two-dimensional (2D)-material-based photodetectors have recently received great attention due to their potentials in developing ultrathin and highly compact devices. Avalanche photodiodes (APDs) are widely used in a variety of fields such as optical communications and bioimaging due to their fast responses and high sensitivities. However, conventional APDs based on bulk materials are limited by their relatively high dark current. One solution to tackle this issue is by employing nanomaterials and nanostructures as the active layers for APDs. In this study, we proposed and fabricated an atomically-thick APD based on heterojunctions formed by 2D transition metal dichalcogenides (TMDs). A typical device structure was formed by stacking a semiconducting monolayer WS2 onto two metallic few-layer MoTe2 flakes. Due to the Schottky barrier formed between the TMD layers and their atomic thicknesses, the dark current of the APD is greatly reduced down to 93 pA. In addition, the APD can operate through a broad spectral range from visible to near-infrared region, with a responsivity of 6.02 A/W, an external quantum efficiency of 1,406%, and an avalanche gain of 587. We believe that the 2D APD demonstrated here provides a feasible approach for developing all-2D optoelectronic devices with simultaneous high-sensitivity and low noise.

High-Speed and High-Responsivity Silicon/Black-Phosphorus Hybrid Plasmonic Waveguide Avalanche Photodetector

“…where V bias is the applied bias voltage, V b is the electric breakdown voltage, and n is the index corresponding to the ionization rate. 40,41 Although the theoretical model is extracted from the silicon avalanche photodiodes, 42 similar trends are observed for the present BP APD, as shown by the fitting curve with n = 8.3 in Figure 4d. The photocurrents of the PDs were characterized for both wavelengths of 1.55/1.95 μm by using the calibrated optical transmission system (see Experimental Methods and Supplementary Note 4).…”

“…Because there is no saturated region in the dark-current curve for the present PD, we set the saturation current I sat as the current when the avalanche process starts to happen, and thus, I sat = I cr . The multiplication factor M is also fitted by the following function: where V bias is the applied bias voltage, V b is the electric breakdown voltage, and n is the index corresponding to the ionization rate. , Although the theoretical model is extracted from the silicon avalanche photodiodes, similar trends are observed for the present BP APD, as shown by the fitting curve with n = 8.3 in Figure d.…”

Engineering sensitivity and spectral range of photodetection in van der Waals materials and hybrids

“…2D hybrid heterostructures have the ability to reduce the dark current, which is otherwise a limiting factor to obtain high detectivity. By stacking monolayer WS 2 between two sheets MoTe 2 , Tenghui Ouyang et al [166] demonstrates suppression of dark current to 90 pA. In this manner, the avalanche photodiode is configured as two back-to-back Schottky barriers formed at WS 2 -MoTe 2 heterojunctions which assist in reducing the dark current and their device exhibits detectivity limits of 10 9 Jones.…”

The Thermal and Electronic Properties of the Lateral Janus MoSSe/WSSe Heterostructure

“…It is found that MoSe 2 has strong light absorption capacity and photoelectric conversion efficiency (close to 10%) in the range of visible light and has a great application prospect in photovoltaic devices (Ma et al, 2011;Shi et al, 2013;Liu et al, 2016a). All these remarkable performances of the 2D materials present advanced applications in metal-ion batteries Sun and Schwingenschlögl, 2021b), photocatalyst (Ong, 2017;Ren et al, 2019;Ren et al, 2021c;Agarwal et al, 2021), photodiode (Ouyang et al, 2021), light emitting devices (Ren et al, 2021d), etc.…”