Continuous narrow-band amplification tuning effect at terahertz frequencies in double-quantum-well resonant tunneling nanostructures

Abstract

High-frequency response properties of single and double-quantum-well resonant tunneling diodes (RTD) are examined in a wide frequency range, up to terahertz (THz) frequencies, on the base of proposed quantum theory. Numerical solutions of time-dependent Schrödinger equations with open-system boundary conditions in an external electromagnetic field are performed. The numerical solutions take into account the influence of bias DC voltage on electronic states in RTD with finite height and width of barriers both for monoenergetic and for Fermi-distributed electrons in emitter and collector parts of structures. We show that the presence of an additional level in double-quantum-well structures breaks the response symmetry and leads to selective narrow-band frequency amplification, as well as to the effect of amplification frequency tuning at THz frequencies by variation of applied bias voltage. These phenomena predict an increase of gain coefficient and open new perspectives for engineering of novel types of THz oscillators and other high-frequency units.