On-chip GaN Vacuum Electron Devices

On-chip vacuum electron devices that operate by cold field emission have the potential to combine advantages of traditional vacuum electron devices (e.g. vacuum tubes), such as robustness in harsh environments and high frequency operation, together with those of modern solid-state devices, such as size, integrability, and energy efficiency. By shrinking the vacuum or “air” channel to nanoscale dimensions well below the electron mean free path in air, these devices can operate at ambient pressures while maintaining the physical advantages of ballistic vacuum transport. Here, we present lateral gallium nitride (GaN) semiconductor nanogap field emission diodes that exhibit ultra-low turn-on voltage, high field-emission current, and that operate in air. The fabrication of these nanoscale devices is enabled by a two-step top-down etching approach allowing for the necessary sidewall verticality and surface smoothness. We present on the field emission characteristics of these devices at various nanogap sizes and operating pressures and temperatures. These devices also show promise for sensitive UV photodetection. These results provide critical new insights into the behavior of this new class of devices and point to future challenges and opportunities.