Self-Powered Sb2Te3/MoS2 Heterojunction Broadband Photodetector on Flexible Substrate from Visible to Near Infrared

Abstract

Van der Waals (vdWs) heterostructures, assembled by stacking of two-dimensional (2D) crystal layers, have emerged as a promising new material system for high-performance optoelectronic applications, such as thin film transistors, photodetectors, and light-emitters. In this study, we showcase an innovative device that leverages strain-tuning capabilities, utilizing a MoS₂/Sb₂Te₃ vdWs p-n heterojunction architecture designed explicitly for photodetection across the visible to near-infrared spectrum. These heterojunction devices provide ultra-low dark currents as small as 4.3 pA, a robust photoresponsivity of 0.12 A W^-1, and reasonable response times characterized by rising and falling durations of 0.197 s and 0.138 s, respectively. These novel devices exhibit remarkable tunability under the application of compressive strain up to 0.3%. The introduction of strain at the heterojunction interface influences the bandgap of the materials, resulting in a significant alteration of the heterojunction's band structure. This subsequently shifts the detector's optical absorption properties. The proposed strategy of strain-induced engineering of the stacked 2D crystal materials allows the tuning of the electronic and optical properties of the device. Such a technique enables fine-tuning of the optoelectronic performance of vdWs devices, paving the way for tunable high-performance, low-power consumption applications. This development also holds significant potential for applications in wearable sensor technology and flexible electro-optic circuits.

Keywords: 2D materials; broadband; flexible substrate; photodetector; photonic integrated circuits; self-powered.

Figure 1

Sb₂Te₃/MoS₂ heterostructure photodetector. (a) A schematic representation of the Sb₂Te₃/MoS₂ van der Waals heterojunction photodetector. (b) The false colored SEM image of the Sb₂Te₃/MoS₂ heterostructure device. (c) The band structures of the vdW layered MoS₂/Sb₂Te₃ heterojunction. (d) The I–V characteristics of the Sb₂Te₃/MoS₂ van der Waals heterojunction under −0.75 to 0.75 V bias voltage in a dark environment. The blue curve illustrates the linear plot, while the red curve represents the log scales.

Figure 2

Photovoltaic characteristics of the Sb₂Te₃/MoS₂ van der Waals heterojunction. (a) The I–V characteristics of the Sb₂Te₃/MoS₂ heterojunction under different optical wavelengths with the same illumination power of 0.55 μW. (b) Delineates the regime outlined in the I–V characteristics, specifically ranging from −0.2 V to 0.2 V. (c) The measured photoresponsivity at different wavelengths (500 nm, 600 nm, 700 nm, 800 nm, and 900 nm), with the same illumination power of 0.55 μW under −0.2 to 0.2 V bias voltage. (d) The measured photocurrent at 500 nm in three different power levels: 0.55 μW, 2.01 μW, and 3.85 μW, respectively. (e) The measured photoresponsivity at 500 nm in three different power levels: 0.55 μW, 2.01 μW, and 3.85 μW, respectively. Photoresponsivity was observed and increased proportionally to the optical power under −0.75 to 0.75 V bias voltage. (f) Responsivity by sweeping the wavelength under 0 and 0.1 V bias from 500 to 900 nm with a step size of 10 nm, which indicates a broad wavelength response.

Figure 3

Strain-dependent photoresponse of the Sb₂Te₃/MoS₂ van der Waals heterojunction. (a,b) The I–V characteristic of the device was measured under varying strains without illumination on a flexible substrate. The dark current decreased substantially as the tensile strain increased. (c) The photoresponsivity of the device was measured under different tensile strains at 500 nm wavelength illumination. As the strain increased, the responsivity decreased, indicating a simultaneous drop in both the photo and dark currents. However, the photocurrent exhibited a more significant decrease. (d–f) The power-dependent responsivity change of the heterojunction device was measured under different strains with a 500 nm laser illumination at 0 V, 0.1 V, and −0.1 V.