Demonstration of a ~40 kV Si Vacuum Transistor as a Practical High Frequency and Power Device

We demonstrate for the first time a vacuum transistor fabricated based upon Si operating in excess of 38 kV applied bias, a voltage normally reserved for high bandgap materials such as SiC and GaN. This is a proof of a concept demonstration of a high-performance vacuum transistor with the potential of having a semiconductor-like footprint. The device consists of a gated field emission array or an electron source, a vacuum drift region and a metal anode. Electrons are emitted from the gated field emission array into vacuum through tunneling, travel through vacuum and are collected at the anode. In this case, the vacuum determines the properties of transport and the high voltage isolation. Important figures of merit: the Baliga, Johnson and power vs. frequency figures of merit (FOMs) are theoretically derived and show the benefits of using a vacuum drift channel, especially for applications which require both high frequency and power. The origin of the improved performance comes from the high critical field of vacuum and most importantly the unbounded nature of the electron velocity due to a lack of scattering.