Development of a vacuum transistor using hafnium nitride field emitter arrays

A vacuum transistor using field emitter arrays was developed to study potential applications as a signal amplifier. We fabricated gated 39 460-tip hafnium nitride field emitter arrays (HfN-FEAs) and evaluated their suitability for use in active devices. The vacuum transistor had a triode structure with a gated HfN-FEA and collector electrode. The device exhibited a collector current of 1.1 mA at an emitter voltage of −58 V, a transconductance of 0.27 mS, and a collector resistance of 2.8 MΩ (yielding a voltage amplification factor of 750). An amplifying circuit based on the present vacuum transistor was designed, and the performance of amplification of an ac signal was evaluated. A voltage gain of 29 dB was obtained with a load resistance of 100 kΩ. A gain bandwidth product of 1 MHz was also obtained.