Analysis of output power characteristics for resonant-tunneling diode terahertz oscillator with cylindrical cavity resonator

Abstract

An increasing number of novel applications has appeared in the previously unexplored frequency range of 0.3–3.0 THz, where sub-mm radio waves meet far-infrared optical waves. Resonant-tunneling diodes (RTDs) are considered as one of the promising compact and coherent room-temperature signal sources for terahertz (THz) applications. In this work, dependencies of output power on the resonator dimensions and output power limitation factors are analyzed for an RTD THz oscillator with a cylindrical cavity resonator, which can oscillate above 2 THz. Analysis of the output power dependencies on radius and height of the cylindrical resonant cavity shows that a decrease in the resonant cavity size could lead to an increase in the output power at a fixed frequency for this type of RTD oscillator. Moreover, in addition to the high-frequency oscillation limit, a rapid decrease in the output power in the lower frequency region was found for oscillator devices with larger RTD mesa areas. Rapid decrease in output power may occur even at frequencies around 1 THz, which could considerably limit the operational range for RTD oscillators with cavity-type resonators. To determine an approach for output power optimization and understand the nature of output power drop at lower frequencies, the output power behavior and connection with resonant cavity parameters were explained in detail. Results of the output power analysis and numerical calculation indicate that for the RTD structure and circular-resonator geometry considered in the present study, output powers up to 45 μW at 1.5 THz and up to 0.25 μW at 2.5 THz could be expected for single oscillator design.