Polarization of far-IR radiation from p-type germanium under uniaxial pressure and strong electric field

Experimental results on the polarization of the far-IR radiation (l=80-120 mm) from p-type germanium under strong uniaxial pressure and heating electric field at liquid-helium temperature are reported. The directions of the polarization and the electric field are shown to be mainly coaxial for samples under pressure and perpendicular to each other for unstrained samples. The possible reasons of this phenomenon are discussed. Experimental results on the polarization of the far-IR radiation (λ=80–120 μm) from p-type germanium under strong uniaxial pressure in a heating electric field at liquid-helium temperature are reported. The directions of the polarization and electric field are shown to be mainly coaxial for samples under pressure and perpendicular to each other for unstrained samples. The possible reasons for this phenomenon are discussed

Effect of Sparse Doping in Barriers on the Energy Structure of Center-Delta-Doped QW

Effect of sparse (presumably background) shallow donor impurity on the energy structure of SiGe/Si quantum well structure delta-doped to the center of the well is studied numerically. The method includes calculation of impurity binding energy. The proposed nanostructure configuration can be used to create tunable optical devices in THz frequency region. © 2019 IEEE

Temperature shift of intraband absorption peak in tunnel-coupled QW structure

An experimental study of the intersubband light absorption by the 100-period GaAs/Al0.25Ga0.75As double quantum well heterostructure doped with silicon is reported and interpreted. Small temperature redshift of the 1–3 intersubband absorption peak is detected. Numerical calculations of the absorption coefficient including self-consistent Hartree calculations of the bottom of the conduction band show good agreement with the observed phenomena. The temperature dependence of energy gap of the material and the depolarization shift should be accounted for to explain the shift. © 2017 Elsevier B.V

Hydrogenic Impurity States in a Delta-Layer Within Quantum Wells in a Transversal Electric Field

The effect of a transversal electric field on the impurity binding energy and the energy differences between the space-quantized subbands of center delta-doped SiGe/Si quantum well structure is studied numerically with a self-consistent method. The result is explained in terms of the concurrent effects of impurity ionization and the applied field. The predicted phenomenon can be used to tune the energy distances and, accordingly, the working frequencies of possible optical devices. © 2020 IEEE

Impurity binding energy for delta-doped quantum well structures

ABSTRACT: The binding energy of an impurity delta layer situated either in the centre or at the edge of a quantum well (QW) is theoretically considered for the example of n-type Si0⋅8Ge0⋅2/Si/Si0⋅8Ge0⋅2 QW doped with phosphorus. Calculations are made for the case of not so big impurity concentrations, when impurity bands are not yet formed and it is still possible to treat impurity as isolated ones. It is shown on the base of self-consistent solution of Schrödinger, Poisson and electro-neutrality equations that impurity binding energy is dependent on the degree of impurity ionization and the most noticeably for the case of edge-doped QWs

Electronic structure and optical properties of triangular GaAs/AlGaAs quantum dots: Exciton and impurity states

Electronic structure and optical properties in equilateral triangular GaAs/Al0.3Ga0.7As quantum dots are studied extensively. The effects of donor and acceptor impurity atoms positioned in the orthocenter of the triangle, as well as of the external DC electric field are taken into account. Binding energies of the impurity, exciton energies, interband photoluminescence peak positions as well as linear and non-linear optical properties in THz range caused by transitions between excitonic states are calculated and discussed. © 2015 Elsevier B.V. All rights reserved

Background impurities in Si0.8 Ge0.2/Si/Si0.8 Ge0.2 n-type δ-doped QW

Additional (residual) impurities in the barriers change the energy profile of a quantum well. This means that they alter the ionization energy for the impurity delta layer situated within the quantum well. In turn, this is accompanied by the change of a V-shaped quantum well created by ionization of the delta layer. All of this is the subject of studies presented in this article. It has been shown that the most dramatic are the changes in the difference between the space-quantized energy levels for an edge-doped quantum well. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Electronic structure and optical properties of triangular GaAs/AlGaAs quantum dots: Exciton and impurity states

Electronic structure and optical properties in equilateral triangular GaAs/Al0.3Ga0.7As quantum dots are studied extensively. The effects of donor and acceptor impurity atoms positioned in the orthocenter of the triangle, as well as of the external DC electric field are taken into account. Binding energies of the impurity, exciton energies, interband photoluminescence peak positions as well as linear and non-linear optical properties in THz range caused by transitions between excitonic states are calculated and discussed. (C) 2015 Elsevier B.V. All rights reserved