Because the properties of terahertz(THz) eletromagnetic waves are its ability to penetrate non-conducting material and be absorbed in conducrive material, THz technology can be applied to various industries such as food inspection and security.
Among the THz emitter, plasma wave transistor(PWT) has advantages of its compatibility with very large scaled integration(VLSI) because PWT is based on field effect transistor(FET) structure. Even if silicon is the most suitable material for making PWT THz emitter in terms of low cost, the Si-based PWT may be hard to be produced due to its low channel mobility. Strained Si(sSi) can break through mobility limitation and make possible to produce PWT.
In the PWT theory, by biasing suggicietly large gate bias and making high density ballistic channel, the collective behavior of electrons, which can be called plasma wave, can be represented as plasma wave velocity s. This electron density oscillation makes additional electric field between source and drain and there comes voltage difference.
With proper boundary conditions at source and drain, we can us PWT as THz emitter and detector.
In case of emitter, we should set AC short boundary condition in the source region so the initial oscillation of plasma wave starts from source side. Also, Ac open condition should be applied drain region so that the oncoming plasma wave toward drain side reflects.
In case of detector, we should set AC open boundary condition in the source region and AC short boundary condition in the drain region.