Bipolar Junction Transistor Exhibiting Excellent Output Characteristics with a Prompt Response against the Selective Protein

Bipolar junction transistors (BJTs), the basic building blocks of integrated circuits, are deployed to control switching applications and logic operations. However, as the thickness of a conventional BJT device approaches a few atoms, its performance decreases substantially. The stacking of atomically thin 2D semiconductor materials is advantageous for manufacturing atomically thin BJT devices owing to the high carrier density of electrons and holes. Here, an atomically thin n–p–n BJT device composed of heavily doped molybdenum ditelluride (n-MoTe₂) and germanium selenide (p-GeSe) sheets stacked over each other by van der Waals interactions is reported. In a common-emitter configuration, MoTe₂/GeSe/MoTe₂ BJT devices exhibit a considerably high current gain (β = I_c /I_b = 29.3) at V_be = 2.5 V. The MoTe₂/GeSe/MoTe₂ BJT device is employed to detect streptavidin biomolecules as analytes within <10 s. The real-time response of the functionalized BJT device is examined at various concentrations of streptavidin biomolecules ranging from 250 to 5 pm. Such vdW BJT devices can trigger the development of state-of-the-art electronic devices that can be used as biosensors to detect the various kinds of target DNA and proteins like spike protein of Covid-19.