WS₂/GeSe/WS₂ Bipolar Transistor-Based Chemical Sensor with Fast Response and Recovery Times

Vertical heterostructures of transition-metal dichalcogenide semiconductors have attracted considerable attention and offer new opportunities in electronics and optoelectronics for the development of innovative and multifunctional devices. Here, we designed a novel and compact vertically stacked two-dimensional (2D) n-WS₂/p-GeSe/n-WS₂ van der Waals (vdW) heterojunction bipolar transistor (2D-HBT)-based chemical sensor. The performance of the 2D-HBT vdW heterostructure with different base thicknesses is investigated by two configurations, namely, common-emitter and common-base configurations. The 2D-HBT vdW heterostructure exhibited intriguing electrical characteristics of current amplification with large gains of α ≈ 1.11 and β ≈ 20.7. In addition, 2D-HBT-based devices have been investigated as chemical sensors for the detection of NH₃ and O₂ gases at room temperature. The effects of different environments, such as air, vacuum, O₂, and NH₃, were also analyzed in dark conditions, and with a light of 633 nm wavelength, ultrahigh sensitivity and fast response and recovery times (6.55 and 16.2 ms, respectively) were observed. These unprecedented outcomes have huge potential in modern technology in the development of low-power amplifiers and gas sensors.