BGFETs

BGFET, short for back-gate field-effect transistor, is a type of field-effect transistor in which the gate electrode is located on the opposite side of the insulating substrate from the conducting channel. In typical BGFETs, the channel rests on a thin dielectric on top of a doped silicon substrate, which itself acts as a global back gate. This arrangement allows the substrate to modulate the channel conductance by applying a gate voltage.

Operation in a BGFET relies on capacitive coupling between the back gate and the channel. Applying a gate voltage induces charge carriers in the channel, changing the source-drain current. Materials such as graphene, transition metal dichalcogenides (for example MoS2), and other two-dimensional semiconductors are commonly used as the channel material. Graphene-based BGFETs often display ambipolar transfer characteristics, with limited current suppression due to graphene’s lack of a sizable bandgap, while 2D semiconductors can offer higher on/off ratios.

Fabrication typically involves placing the channel material on a dielectric layer atop a doped silicon wafer, followed by patterning of source and drain electrodes. Common channel materials include graphene, MoS2, WS2, and black phosphorus. The back-gate geometry is compatible with standard microfabrication but can introduce substrate-related charge traps and variability from wafer to wafer.

Applications of BGFETs are prominent in research on nanoelectronics and sensing, especially with 2D materials, where the high surface-to-volume ratio enhances sensitivity. They are often used as testbeds for studying gating effects, device physics, and simple, low-cost sensor architectures. See also field-effect transistor, graphene FET, MoS2 FET, back-gate gating.