The non-linear terahertz response of hot electrons in low-dimensional semiconductor superlattices: Suppression of the polar-optical phonon scattering

Abstract

……We study the response of low-dimensional semiconductor superlattices to strong terahertz fields on condition of a strong suppression of inelastic scattering processes of electrons caused by the polar-optical phonons. For our study we employ a balance equations approach which allows investigating the response of the superlattices to strong terahertz fields taking account of both the inelastic and the strongly pronounced elastic scattering of electrons. Our approach provides a way to analyze the influence of the Bloch dynamics of electrons in a superlattice miniband side by side with the effects of the electron heating on the magnitude and the frequency dependence of a superlattice current responsivity in the terahertz frequency band. Our study shows that the suppression of the inelastic scattering caused either by a reduction of the superlattice dimensionality by lateral quantization or by a strong magnetic field application can give rise to a huge enhancement of the current responsivity. This enhancement can be interpreted in terms of the well pronounced electronic bolometric effect occurring due to the efficient electron heating in the low-dimensional superlattices by the incident terahertz fields.

Mechanism of resonant enhancement of electron drift in nanometer semiconductor superlattices subjected to electric and inclined magnetic fields

“…Need for the latter arose because some researchers seemed to remain unpersuaded by the arguments in the Letter 37 and had been explicitly 38,71,72 or implicitly 39,41 continuing to refer to the original conjecture 19,21 of chaotic diffusion as the mechanism underlying the resonant enhancement of electron transport. It also seems that a huge number of references to this exciting-sounding but incorrect idea done before the publication of the Letter 37 and its continued promulgation 38,39,41,71,72 after it keep misleading researchers in other areas [73][74][75][76][77][78][79] , who still mention the resonant enhancement of electron drift 19,21,26 as a manifestation of "chaotic dynamics in semiconductor SLs" 73,75,76,78,79 or as the ability of non-KAM chaos to "enhance electronic transport in semiconductor superlattices" 74,77 .…”

Controlling the harmonic conversion efficiency in semiconductor superlattices by interface roughness design

“…As a matter of fact, previous experimental work has focused on trying to understand how the dephasing mechanisms of Bloch oscillations and the electron mobility are related specifically to (elastic) interface roughness scattering [16,17]. Special attention has been given to nonlinear balance-equation transport dynamics [6,18], which has been systematically employed to make prediction for different terahertz amplification and generation schemes [14,19]. This approach-which follows from Boltzmann transport equation-allows one to take into account scattering processes which change both momentum and energy but it depends heavily on fitting the analytical equations to experimental data or assuming purely phenomenological parameters [20].…”

“…We should note that a domain-free generation is possible if the input field frequency belongs to the high-frequency part of the terahertz range. Alternatively, the suppression of space-charge instabilities holds either for a SSL oscillator with a microwave pump or the special design of a structure that compensates their effects [19,23]. Future work will take into consideration domain effects using a more complete microscopic NEGF approach.…”