Terahertz response of resonant tunneling diodes

We have measured the broad-band terahertz response of state of the art InGaAs/AlAs and InAs/AlSb resonant tunneling diodes from 180 GHz to 3.6 THz using the free-electron lasers at UCSB. A tungsten whisker antenna in a conventional probe station is used to couple the far-infrared radiation into the device. Normalizing the resonant tunneling response with the off-resonant response allows us to circumvent the much slower RC time constant of the device and consequently enables a measurement of the relaxation time due to the quantum inductance.