Fast terahertz detectors with spectral tunability based on quantum Hall Corbino devices

We present THz photoconductivity measurements on Corbino-shaped GaAs∕AlGaAs heterostructures. The THz source is a pulsed p-Ge laser, which provides photon frequencies of 1.7THzto2.5THz (corresponding to wavelengths of 180–120μm). We investigate the relaxation process from the dissipative state to the quantum Hall state time-resolved and find that the relaxation time depends on the applied voltage and on the mobility of the sample. Relaxation times of approximately 10ns to over 200ns are observed. A simple picture is suggested to explain the results. In addition, spectrally resolved measurements are discussed. The short response time and the useful spectral selectivity together with the high sensitivity make QH devices promising for high-performance THz detectors.