THz oscillators using resonant tunneling diodes

We report on our recent results of terahertz oscillators with resonant tunneling diodes (RTDs) at room temperature. By a structure with high current density and small capacitance, a fundamental oscillation at 831 GHz was obtained in GaInAs/AlAs double-barrier RTDs integrated with slot antennas. A comparison with theoretical analysis shows a possibility of electron transition from the Γ to L bands in the collector transit region which brings about a long transit time. By suppressing this transition with a graded emitter structure, a fundamental oscillation up to 1.04 THz was obtained at room temperature. This is the first oscillation over 1 THz of a room-temperature electronic single oscillator. For high output power, an offset-fed slot antenna and high current density was used, and 150 μW at 270 GHz with the DC-to-RF conversion of 1.9% was obtained. Power combining in array configuration, frequency change with bias current, and direct frequency modulation were also shown.