Field Effect-Controlled Space-Charge Limited Emission Triode With Nanogap Channels

Nanoscale vacuum (airgap) channels have garnered attention as conduits for ballistic electron transport even under ambient atmospheric conditions. To date only single nanogap devices that cannot be integrated have been developed. This report presents a nanoscale space charge limited field emission (SCL-FE) triode based on a combination of one lateral and two vertical nanoscale airgaps in a Metal-oxide-semiconductor (MOS). Two identical MOS-shared p-Si substrates are separated by a $\sim 50$ -nm-wide etched trench to create a combined lateral bidirectional SCL-FE metal–air device and dual vertical nanoscale vacuum diodes. The lateral device provides bidirectional SCL-FE electron current, and the vertical devices provide rectifying behavior for carrier transport. The ballistic trajectories of electrons within the nanoscale airgap can be controlled by driving the two MOSs in different operational regimes. The triode operates at a low voltage of $\sim 2$ V and has an emission-capture efficiency of up to $\sim 95$ %, with a total emission current density of $\sim 2\times 10^{3}$ A/cm2.