Resonant Tunneling and Quantum Cascading for Optimum Room-Temperature Generation of THz Signals

We report on the results of a numerical study of quantum transport in ZnSe-based resonant-tunneling diodes (RTDs) and quantum cascade oscillators (QCOs) with fixed and unequal barrier heights. It is found that the negative differential resistance exists up to room temperature in the current–voltage characteristics of the RTD and QCO devices with unequal barrier heights. Further, we demonstrate that QCOs with unequal barrier heights have a better frequency and power performance characteristics compared with RTDs and are more beneficial for high-power terahertz generation at room temperature. For the best QCO device with 100 periods of quantum cascading, a maximum output power of ~7–9 $\mu \text{W}$ for the operating frequency range from 0.1 to ~6 THz at room temperature was achieved.