Sub-terahertz AlN/GaN resonant tunneling diode oscillators using split-ring resonators integrated with bow-tie antennas

We developed sub-terahertz oscillators employing GaN-based resonant tunneling diodes (RTDs) grown on semi-insulating c-plane GaN substrates using metal-organic chemical vapor deposition. The RTDs incorporated a GaN quantum well and AlN double barriers, with an InGaN layer as part of the collector-side spacer. This InGaN spacer significantly enhanced the resonant tunneling current compared to conventional GaN-only spacers, achieving a peak current density of up to 622 kA/cm2, peak-to-valley current ratio of 1.56, and a maximum negative differential conductance of 7.1 mS/μm2. The oscillator structure featured split-ring resonators integrated with bow-tie antennas, which improved the radiation efficiency on the low-frequency side, facilitating effective electromagnetic wave emission at an intended oscillation frequency. The fabricated AlN/GaN-RTD oscillators exhibited sub-terahertz oscillations in the 88–104 GHz frequency range. These findings contribute to advancing high-frequency sources for sub-terahertz and terahertz applications.