Fast Response GaN Nanoscale Air Channel Diodes with Highly Stable 10 mA Output Current toward Wafer‐Scale Fabrication (Adv. Sci. 17/2023)

Abstract

GaN NaNoscale air chaNNel DioDesIn article number 2206385 by Mo Li and co-workers, a vertical GaN nanodiode with a 50 nm air channel is reported, fabricated using IC-compatible technologies, with a record field emission current of 11 mA@10 V. Notably, the device displays outstanding stability and fast switching characteristics with a sub-10 ns response time. Additionally, the temperaturedependent performance can guide the design of nano-air-channel-devices for applications in extreme conditions.

β-Ga2O3 Air-Channel Field-Emission Nanodiode with Ultrahigh Current Density and Low Turn-On Voltage

“…Concurrently, there is no heat generation or dielectric breakdown in the vacuum channel. Therefore, vacuum electronic devices based on field emission are still indispensable in numerous important applications, particularly in the harsh environments (e.g., radiation, high temperature) including nuclear, aerospace, automotive industries, etc. − Fortunately, the development of micro- and nanoscale manufacturing technologies has greatly eased the main problems with vacuum electronic devices in the early stages. , By scaling the emission tips down to nanoscale, cold cathodes are allowed, and efficient field emission can be achieved at even very low bias voltages. In addition, the precisely fabricated nanoscale gaps smaller than the mean-free path (MFP) of electrons (∼200 nm) at atmospheric pressure can eliminate the necessity of high vacuum, which reduces the device size and greatly ease the burden for the vacuuming accessories. , Notably, excellent field-emission performances have been achieved recently by wide bandgap semiconductors such as SiC, GaN, and ZnO. ,, Very impressively, the study on robust, on-chip GaN nanodiodes with air channels has exhibited ultralow turn-on voltage (0.24 V @ 100 pA) .…”

“…Current saturation can be observed from ∼10 V bias voltage and beyond. Field-emission current saturation has been observed in varieties of nonmetallic materials, ,− but the exact reason is still controversial. In our case, the main reason is very likely the velocity saturation of electrons under strong electrical field in β-Ga 2 O 3 NW (see Supplementary IV).…”

“…For a fair comparison, the chosen works are all about diodes based on field emission with nanoscale air gaps that are smaller than the MFP of electrons in air (see Supplementary X). Figure plots the comparison in the turn-on voltage V on , ,,,,− and the open dots in the figure mean the nanodiodes in these works need an ambient vacuum for measurement. Obviously, the V on of the β-Ga 2 O 3 nanodiode is comparable to the best reported air-channel diodes based on either metals or semiconductors, indicating the huge potentials for β-Ga 2 O 3 in vacuum electronics.…”

“…2−7 Fortunately, the development of micro-and nanoscale manufacturing technologies has greatly eased the main problems with vacuum electronic devices in the early stages. 8,9 By scaling the emission tips down to nanoscale, cold cathodes are allowed, and efficient field emission can be achieved at even very low bias voltages. In addition, the precisely fabricated nanoscale gaps smaller than the mean-free path (MFP) of electrons (∼200 nm) at atmospheric pressure can eliminate the necessity of high vacuum, which reduces the device size and greatly ease the burden for the vacuuming accessories.…”