High frequency impact ionization and nonlinearity of photocurrent induced by intense terahertz radiation in HgTe-based quantum well structures

Abstract

We report on a strong nonlinear behavior of the photogalvanics and photoconductivity under excitation of HgTe quantum wells (QWs) by intense terahertz (THz) radiation. The increasing radiation intensity causes an inversion of the sign of the photocurrent and transition to its superlinear dependence on the intensity. The photoconductivity also shows a superlinear raise with the intensity. We show that the observed photoresponse nonlinearities are caused by the band-to-band \emph{light} impact ionization under conditions of a photon energy less than the forbidden gap. The signature of this kind of impact ionization is that the angular radiation frequency $\omega =2\pi f$ is much higher than the reciprocal momentum relaxation time. Thus, the impact ionization takes place solely because of collisions in the presence of a high-frequency electric field. The effect has been measured on narrow HgTe/CdTe QWs of 5.7\,nm width; the nonlinearity is detected for linearly and circularly polarized THz radiation with different frequencies ranging from $f=0.6$ to 1.07\,THz and intensities up to hundreds of kW/cm${}^2$. We demonstrate that the probability of the impact ionization is proportional to the exponential function, $\exp (-E_0^2/E^2)$, of the radiation electric field amplitude $E$ and the characteristic field parameter $E_0$. The effect is observable in a wide temperature range from 4.2 to 90\,K, with the characteristic field increasing with rising temperature.

References in corpus (17)

• Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
• Quantum Spin Hall Insulator State in HgTe Quantum Wells
• Floquet Topological Insulator in Semiconductor Quantum Wells
• First principles calculations of the Shift Current Bulk Photovoltaic Effect in Ferroelectrics
• Band structure of semimagnetic Hg1-yMnyTe quantum wells
• Room temperature high frequency transport of Dirac fermions in epitaxially grown Sb_2Te_3 based topological insulators
• THz-pump -- THz-probe spectroscopy of semiconductors at high field strengths
• Magneto-Gyrotropic Photogalvanic Effects in Semiconductor Quantum Wells
• Giant spin-polarized current in a Dirac fermion system at cyclotron resonance
• Classical ratchet effects in heterostructures with a lateral periodic potential
• Helicity sensitive terahertz radiation detection by field effect transistors
• Photogalvanic probing of helical edge channels in 2D HgTe topological insulators
• Dynamical birefringence: Electron-hole recollisions as probes of Berry curvature
• Circular photogalvanic effect in HgTe/CdHgTe quantum well structures
• Optical emission of graphene and electron-hole pair production induced by a strong THz field
• Ballistic geometric resistance resonances in a single surface of a topological insulator
• Doubly dressed bosons - exciton-polaritons in a strong terahertz field

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• Roles of band gap and Kane electronic dispersion in the THz-frequency nonlinear optical response in HgCdTe
• Bleaching of the Terahertz Magneto-Photogalvanic Effect in CdHgTe Crystals with Kane Fermions
• Impact ionization induced by terahertz radiation in HgTe quantum wells of critical thickness
• Strongly nonlinear Bernstein modes in graphene reveal plasmon-enhanced near-field magnetoabsorption
• Positive Terahertz Photoconductivity in CdHgTe Under Hydrostatic Pressure