Omega-Gate Silicon Nanowire Geometric Diodes with Reconfigurable Self-Switching Operation and THz Rectification

Geometric diodes (GDs) represent a relatively unconventional class of diode that produces an asymmetric current response through carrier transport in an asymmetric geometry. Synthesized from the bottom up, Si nanowire-based GDs are three-dimensional, cylindrically symmetric nanoscale versions capable of room-temperature rectification at GHz-THz frequencies with near zero-bias turn-on voltages. Here, by fabricating three-terminal n-type Si nanowire GDs with axial contacts and an omega-gate electrode, a distinct class of reconfigurable self-switching geometric diodes (SSGDs) is reported. Single-nanowire SSGD device measurements demonstrate a significant dependence of diode current and polarity on gate potential, where the diode polarity reverses at a gate potential of approximate to-1 V under specific grounding conditions. Finite-element modeling reproduces the experimental results and reveals that the gate potential-in combination with the morphology and dopant profile-produces an asymmetric potential along the nanowire axis that changes asymmetrically with axial bias, altering the effective conductive channel within the nanowire to yield diode behavior. The self-switching effect is retained in two-terminal SSGD devices, and modeling demonstrates that both three-terminal and two-terminal devices support rectification through THz frequencies. The results reveal a new mechanism of operation for nanowire-based GDs and characterize a new type of self-switching diode with reconfigurable polarity. Asymmetric silicon nanowires are fabricated into three-terminal devices using an omega gate electrode. The devices exhibit self-switching diode behavior, an effect resulting from the combination of asymmetric dopant profile and asymmetric geometry. The polarity of the diodes can be reconfigured by choice of gate potential, and the structures have the capacity to operate into the THz regime.image

Automated summary

This study reports the fabrication of three-terminal n-type Si nanowire geometric diodes (GDs) that exhibit self-switching diode behavior. The diode current and polarity show a significant dependence on gate potential, and under specific grounding conditions, the polarity of the diodes reverses. Finite-element modeling reveals that the gate potential, along with the morphology and dopant profile, produces an asymmetric potential along the nanowire axis, leading to an asymmetric change in the effective conductive channel and resulting in diode behavior. These findings characterize a new mechanism of operation for nanowire-based GDs and demonstrate a new type of self-switching diode with reconfigurable polarity.