Generalized Analysis of Output-Power Limitations of Resonant-Tunnelling-Diode Oscillators With Symmetrical Slot Antennas

In this article, we present optimization results for the symmetrical-slot-antenna resonant-tunnelling-diode (RTD) oscillators with account of relevant antenna losses and RTD parasitics. The results are in good agreement with available experimental data. The frequency roll-off of the output power has a complicated dependence on the oscillator parameters and does not exhibit a distinct dominant mechanism responsible for it. However, the roll-off is much steeper for lower-current-density RTDs, with much better performance of high-current-density RTDs not only at terahertz (THz) but also at sub-THz frequencies. The required minimum RTD-mesa area for optimized oscillators remains in an acceptable range for common fabrication technology: $\approx 0.1\text{--}0.2\,\mu\text {m}^{2}$.