Impact ionization induced by terahertz radiation in HgTe quantum wells of critical thickness

28 Jan 2020  ·  Hubmann S., Budkin G. V., Urban M., Bel'kov V. V., ~Dmitriev A. P., Ziegler J., Kozlov D. A., Mikhailov N. N., Dvoretsky S. A., Kvon Z. D., Weiss D., Ganichev S. D. ·

We report on the observation of terahertz (THz) radiation induced band-to-band impact ionization in \HgTe quantum well (QW) structures of critical thickness, which are characterized by a nearly linear energy dispersion. The THz electric field drives the carriers initializing electron-hole pair generation... The carrier multiplication is observed for photon energies less than the energy gap under the condition that the product of the radiation angular frequency $\omega$ and momentum relaxation time $\tau_{\text l}$ larger than unity. In this case, the charge carriers acquire high energies solely because of collisions in the presence of a high-frequency electric field. The developed microscopic theory shows that the probability of the light impact ionization is proportional to $\exp(-E_0^2/E^2)$, with the radiation electric field amplitude $E$ and the characteristic field parameter $E_0$. As observed in experiment, it exhibits a strong frequency dependence for $\omega \tau \gg 1$ characterized by the characteristic field $E_0$ linearly increasing with the radiation frequency $\omega$. read more

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Mesoscale and Nanoscale Physics