Simulation and theoretical analysis of a photoconductive vacuum microelectronic device

This paper provides the simulation and theoretical analysis of a photoconductive vacuum microelectronic device (PVMD), which enables the possibility of bridging the terahertz gap that is not previously possible in traditional vacuum microelectronics, and can operate with high photocurrent density that can be modulated by the laser beat frequency optical field. Here, a conceptual vacuum diode and triode is modeled and simulated with particle in cell simulation softwares to calculate electric fields and electron trajectories. The numerical simulations show that a φ2 μm vacuum channel in a volume of 5 μm × 5 μm × 5 μm diode could transport electron with current density up to 880 A/cm², which means that diode can generate a relatively high terahertz current signal when beat frequency is in terahertz range (0.1-2 THz); For triode, the cathode to gate capacitance can be approximated using software calculation which can get a capacitance less than 1.0 ×10⁻¹⁷ F, then using a triode transconductance that is close to 4.38 μS, we can derive the cut off frequency to be ∼ 65 GHz. And this can be further expanded to the terahertz band when the distributed amplifier scheme is put forward. Furthermore, a modified small signal circuit model was also proposed to analyze the amplification behavior and frequency response of the vacuum triode device. A voltage gain equation was realized after parasitic capacitance was considered according to Miller's Theorem. In summary, this device has the potential to foster a new class of integrated devices which can help to generate high power terahertz signal or radiation.