Time response of a highly sensitive and tunable THz detector using the quantum hall effect

Abstract

We studied time evolution of photoexcited carriers induced by cyclotron resonance in a quantum Hall system. The relaxation of the photoconductivity shows non-single exponential time dependence with relaxation time of the order of milliseconds. It is in contrast to the time evolution in the excitation, which shows single exponential behaviour. The difference between time dependence of the relaxation and the excitation systematically changes with the Landau level-filling factor. The observations suggest that the carriers are repeatedly captured into the localized states and re-excited into the delocalised states. Since the long relaxation time of photoexcited carriers leads to strong photoconductivity and the relaxation time has a positive dependence on electron mobility, the high electron mobility will contribute to the sensitivity of the THz detector.