Numerical analysis for resonance properties of plasma-wave field-effect transistors and their terahertz applications to smart photonic network systems

This paper describes the numerical analysis for terahertz electromagnetic-wave oscillation/detection properties of plasma-wave field-effect transistors (PW-FET's) and their applications to future smart photonic network systems. The PW-FET is a new type of the electron device that utilizes the plasma resonance effect of highly dense two-dimensional conduction electrons in the FET channel. By numerically solving the hydrodynamic equations for PW-FET's, the plasma resonance characteristics under terahertz electromagnetic-wave absorption are analyzed for three types of FET's; Si MOSFET's, GaAs MESFET's, and InP-based HEMT's. The results indicate that the InP-based sub-100-nm gate-length HEMT's exhibit the most promising oscillation/detection characteristics in the terahertz range with very wide frequency tunability. By introducing the PW-FET's as injection-locked terahertz-frequency-tunable oscillators and terahertz mixers, a new idea of coherent heterodyne detection utilizing terahertz IF (intermediate-frequency) bands is proposed for the future smart photonic network systems that enable real-time adaptive wavelength routing for add-drop multiplexing. The plasma resonance of PW-FET's by means of different frequency generation based on direct photomixing is also proposed as an alternative approach to injection-locked terahertz oscillation. To realize it, virtual carrier excitations by the polariton having photon energy lower than the bandgap of the channel is a possible mechanism.