Backgated

Backgated refers to electronic devices in which the gate electrode is located on the opposite side of the active channel, typically implemented by using a conducting substrate as the gate with a dielectric in between. In practice, a silicon wafer with oxide acts as a back gate for materials such as graphene, MoS2, or other two-dimensional materials laid on the oxide. The back gate forms a capacitor with the channel, so applying voltage to the substrate modulates the carrier density and the Fermi level in the channel, enabling field-effect control without a separate top-gate electrode.

Back-gated devices are common in basic research and early-stage device studies, where a global gate is convenient for examining intrinsic properties, transport behavior, and gating efficiency of a material system on a uniform dielectric stack. The approach is widely used with graphene and other 2D materials on standard Si/SiO2 substrates, and can also apply to nanowires or thin-film transistors that rely on a substrate-based modulation.

Advantages of back-gating include simple fabrication on conventional substrates, broad compatibility with large-area samples, and the ability to globally tune multiple devices simultaneously. Limitations include lower gate efficiency due to the relatively thick oxide layer, potential charge traps at the oxide–channel interface, and limited ability for localized or high-speed gating. It also provides less flexibility for circuit-level integration compared with top-gating, which uses thin dielectrics and local gate electrodes.

In context, back-gated devices are often contrasted with top-gated devices, where a gate electrode is placed above the channel with a thin dielectric to achieve higher capacitance and more precise, localized control.