Frequency increase in resonant-tunneling-diode terahertz oscillators using optimum collector spacer

We report an increase in oscillation frequency of room-temperature terahertz oscillators using AIAs/InGaAs resonant tunneling diodes (RTDs) with optimized collector spacer thickness. Because of the trade-off relation between the capacitance and electron transit time for the spacer thickness, an optimum thickness exists in terms of the oscillation frequency. The highest frequency in this experiment was 1.42 THz at the optimum spacer thickness of 12 nm with an output power of ~1 μW. A fundamental oscillation at a frequency >2 THz and output power of ~300 μW at 1 THz are theoretically possible by optimized structures of RTD and antenna.