Abstract-Giant terahertz photoconductance of tunneling point contacts

M. Otteneder, Z. D. Kvon, O. A. Tkachenko, V. A. Tkachenko, A. S. Jaroshevich, E. E. Rodyakina, A. V. Latyshev, and S. D. Ganichev


https://journals.aps.org/prapplied/accepted/07074Ae7Z1f17b05b1811dd8e196af92cb8eaeaca

We report on the observation of the giant photoconductance of a quantum point contact (QPC) in tunneling regime excited by terahertz radiation. Studied QPCs are formed in a GaAs/AlGaAs heterostructure with a high-electron-mobility two-dimensional electron gas. We demonstrate that irradiation of strongly negatively biased QPCs by laser radiation with frequency $f=0.69$~THz and intensity 50~mW/cm${}^2$ results in two orders of magnitude enhancement of the QPC conductance. The effect increases with the dark conductivity decrease. It is also characterized by a strong polarization dependence and a drastic reduction of the signal by increasing the radiation frequency to 1.63 THz. We demonstrate that all experimental findings can be well explained by the photon-assisted tunneling through the QPC. Corresponding calculations are in good agreement with the experiment.