Magnetophonon Resonance Research Articles

Optically Detected Magnetophonon Resonances in Quantum Wells

Optically Detected Magnetophonon Resonances in Quantum Wells

Magnetophonon resonance in multimode lattices and two-dimensional structures (DQW)

The experimental results obtained for the magneto-transport in the InGaAs/InAlAs double quantum wells (DQW) structures of two different shapes of wells are reported. The Magnetophonon Resonance (MPR) o was observed for both types of the structures at 77-125K temperatures in the pulsed magnetic field. Four kinds of LO-phonons are taken into account to interpret the MPR oscillations in DQW. The particularity of MPR in DQW is the great number Landau levels caused by SAS-splitting all electron states.

Superlattice magnetophonon resonances in strongly coupledInAs∕GaSbsuperlattices

We report an experimental study of miniband magnetoconduction in semiconducting InAs/GaSb superlattices. For samples with miniband widths below the longitudinal optical phonon energy we identify a new superlattice magnetophonon resonance (SLMPR) caused by resonant scattering of electrons across the mini-Brillouin zone. This new resonant feature arises directly from the drift velocity characteristics of the superlattice dispersion and total magnetic quantisation of the superlattice Landau level minibands.

MAGNETOPHONON RESONANCE IN MnxCdyHg1-x-yTe

The aim of this work is to analyze the band-structure parameters of Mn x Cd y Hg 1- x - y Te (MMCT) alloys by means of Magnetophonon Resonance (MPR) and to compare that obtained for Zn x Cd y Hg 1- x - y Te (ZMCT). MPR was observed for two samples of Mn x Cd y Hg 1- x - y Te (MMCT) (I- x =0.095 and y =0.09, II-0.04 and y =0.19). The measurements of MPR were performed in pulsed magnetic fields at different temperatures ranging from 77 K to 200 K. The several wide maxima are clearly visible on the experimental curves corresponding to four series of peaks. These series are related to three kinds of phonons analogous to ZMCT. The system of MPR peaks in MMCT is shifted significantly to the higher magnetic fields in comparison with the ZMCT resonance curves of approximately the same content of Zn . The value of effective mass obtained by MPR experiment is of 66% greater than those calculated in the framework of three-band Kane model, in which the value of Eg, was extracted from the photoconductivity data.

Magnetophonon oscillations in the negative differential conductance of dilute nitrideGaAs1−xNxsubmicron diodes

We study the nonlinear electron dynamics that occurs in the dilute nitride alloy Ga(AsN) when, in high applied electric fields, conduction electrons gain sufficient energy to approach the energy of the localized N level. This process leads to a strong negative differential conductance (NDC) effect. In a quantizing magnetic field, we observe that the threshold electric field for NDC is resonantly modulated when electrons can relax energy by inter-Landau-level transitions involving the emission of a longitudinal optical phonon. This unusual manifestation of magnetophonon resonance reveals that the mechanism giving rise to NDC is an inherently fast $(<{10}^{\ensuremath{-}12}\phantom{\rule{0.3em}{0ex}}\mathrm{s})$ process of relevance for terahertz electronics.

Hot-electron magnetophonon resonances in quasi-one-dimensional quantum structures

Hot-electron magnetophonon resonances in quasi-one-dimensional quantum structures

Stark magnetophonon resonances in Wannier-Stark localizedInAs∕GaSbsuperlattices

We report an experimental study of high electric field magnetoconduction in semiconducting $\mathrm{InAs}∕\mathrm{GaSb}$ superlattices. This demonstrates that total quantization of the electronic states leads to conduction dominated by a combination of interwell and intrawell processes. The strongest conduction occurs for the triple Stark magnetophonon resonance where resonant interwell tunnelling coincides with (multiple) intrawell longitudinal optical phonon emission.

Magnetophonon resonance of resonant tunneling hot electrons at high magnetic fields

Magnetophonon relaxation of hot electrons injected by resonant tunneling into a wide, undoped drift region is observed by measuring the magnetoresistance. Under resonant tunneling conditions, strong oscillations are observed that are attributed to emission of GaAs and AlAs-like LO phonons. Values for the effective mass of hot electrons are obtained from the resonant magnetic field positions. The effective mass is considerably larger than conduction band edge masses and agrees well with cyclotron resonance measurements at $190\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. Moreover, magneto-oscillations are also observed in the valley current region. These are distinctively different from magnetophonon resonance oscillations and can be explained by inter-Landau-level-tunneling.

Angular dependence of magnetophonon resonances in semiconductor superlattices in tilted magnetic fields

We obtain the angular dependence of magnetophonon resonance (MPR) peaks from longitudinal magnetoconductivities of GaAs/AlAs semiconductor superlattices for longitudinal optical (LO) phonons in tilted magnetic field applied to the superlattice axis. The MPR peaks of both GaAs and AlAs LO phonon modes using the second derivative of the magnetoconductivities including a miniband width and a periodicity of the potential are shown. As the tilt angle of the applied magnetic fields is increased, the MPR peak positions are shifting to higher magnetic strength region whereas the peak amplitudes are decreasing to vanish at the same condition with experiments. Our results are in qualitative good agreement with the experimental results. We also get the resonance fields for the MPR peak numbers of the GaAs and AlAs LO phonon modes as a function of the tilt angles. Furthermore, we obtain the dispersion relations and the density of states (DOS) including a miniband width, a periodicity of the potential and tilt angles of the tilted magnetic fields to explain the appearance of plateau region between neighboring peak amplitudes. The plateau region can be explained by phenomena such as the shifts, the decreases, and the disappearances of the peak amplitudes of the magnetoconductivities and the second derivative of magnetoconductivities of GaAs/AlAs semiconductor superlattices for tilt angles of the applied magnetic fields.

Optical absorption coefficients in two-dimensional semiconductors under strong magnetic field

We calculate the photon absorption coefficient of hot two-dimensional electrons in the presence of a strong magnetic field. The electrons interact strongly with the optical phonons and the acoustic phonons in quantum wells. The dependence of the optical absorption on the magnetic field is obtained by using the quantum mechanical kinetic theory. It is found that the photon absorption spectrum displays a local magnetophonon resonance. The magnetophonon absorption resulting from inelastic scattering between Landau levels is more pronounced at higher temperature. The effect of subband nonparabolicity on the absorption coefficient is also discussed.

Magnetophonon resonance in a GaAs quantum well with AlAs/GaAs superlattice barriers at high filling factors

The magnetotransport of a high-mobility 2D electron gas in single GaAs quantum wells with AlAs/GaAs superlattice barriers is studied at high filling factors. For the selectively doped structures under study in the temperature range from 10 to 25 K, magnetoresistance oscillations periodic in the inverse magnetic field are observed with their frequency being proportional to the Fermi wave vector of the 2D electron gas. The experimental results are explained by the interaction of the 2D electron gas with leaky interface acoustic phonons.

Theoretical study on the optical detection of magnetophonon resonance in semiconductors in tilted magnetic fields

Theoretical study on the optical detection of magnetophonon resonance in semiconductors in tilted magnetic fields

Parallel magnetotransport in multiple quantum well structures

The results of investigations of parallel magnetotransport in AlGaAs/GaAs and InGaAs/InAlAs/InP multiple quantum-well structures (MQWs) are presented. The MQWs were obtained by metalorganic vapor phase epitaxy with different shapes of the QWs, numbers of QWs, and levels of doping. The magnetotransport measurements were performed in a wide region of temperatures (0.5–300 K) and at high magnetic fields up to 30 T (B is perpendicular to and the current is parallel to the plane of the QW). Three types of observed effects are analyzed: the quantum Hall effect and Shubnikov—de Haas oscillations at low temperatures (0.5–6 K) and magnetophonon resonance at higher temperatures (77–300 K).

Effect of Electric Field on the Optically Detected Quantum Magnetophonon Resonances in Semiconductors in a Quantized Magnetic Field

Effect of Electric Field on the Optically Detected Quantum Magnetophonon Resonances in Semiconductors in a Quantized Magnetic Field

Magnetophonon resonance in quantum wells in tilted field: what is concealed behind itsangular dependence?

Magnetophonon resonance in quantum wells in a tilted magnetic fieldB is investigated. Measurements of the Hall coefficient and correspondingly of the carrierconcentration as a functions of magnetic field and temperature are simultaneouslyperformed. It is shown that the experimental data can be interpreted in terms of a greatsensitivity to the effects of varying the two dimensional carrier concentrationns in a certain concentration interval. In other words, the observed angulardependence of the MPR amplitudes is a manifestation of dependence ofns on the magnitudeof the magnetic field B. We believe that such a dependence can be relevant in general for the interpretation ofmagnetotransport in nondegenerate 2D electron gas.

Intersubband lifetime tuning by magnetophonon resonance in GaAs/GaAlAs quantum cascade lasers

Intersubband magneto-phonon resonance in QWs appears as a resonant relaxation of the energy of carriers in excited subbands when a quantizing high magnetic field is applied along the growth axis. The carrier lifetime shows oscillations periodic with the reciprocal of the field. We recently evidenced this effect on the light intensity of GaAs/GaAlAs quantum cascade lasers and focus here on the electron lifetime in the high magnetic field regime. The lifetime vs. magnetic field, derived from the laser threshold current, may be used to probe the electron–phonon coupling strength in this quantum dot like system.

Magnetophonon resonance in high-density high-mobility quantum well systems

We have investigated the magnetophonon resonance (MPR) effect in a series of single GaAs quantum well samples which are symmetrically modulation doped in the adjacent short period AlAs/GaAs superlattices. Two distinct MPR series are observed originating from the $\ensuremath{\Gamma}$ and X electrons interacting with the GaAs and AlAs longitudinal optic (LO) phonons respectively. This confirms unequivocally the presence of X electrons in the AlAs quantum well of the superlattice previously invoked to explain the high electron mobility in these structures [Friedland et al., Phys. Rev. Lett 77, 4616 (1996)]

Tuned transition from a quantum well to a quantum wire investigated by magnetophonon resonance

This article describes experimental investigations of the transition from a two-dimensional electron gas to a quasi-one-dimensional quantum wire by the magnetophonon effect, tuned by Schottky gates in GaAs/AlGaAs. We present a model of the depletion region linked to the gates. The measurements allow the band-edge effective mass to be determined from two to one dimension between 89.5 and 348 K. We performed the measurements with a single, isolated quantum wire in magnetic fields up to 17 T.

Magnetophonon resonance in MnxCdyHg1−x−yTe and ZnxCdyHg1−x−yTe

Magnetophonon resonance (MPR) was studied in Mn0.095Cd0.09Hg0.815Te and Mn0.04Cd0.09Hg0.77Te quaternary solid solution. The fundamental line of MPR is observed at the magnetic field of about 10T. This value is considerably higher than that for ZnxCdyHg1−x−yTe of the same energy gap. The interpretation of this effect is based on sp–d exchange interaction between the spin of free carriers and the localized magnetic moments of the Mn2+ ions.

High-field magnetotransport in a two-dimensional electron gas in quantizing magnetic fieldsand intense terahertz laser fields

We present a combined experimental and theoretical study of interactions betweentwo-dimensional electron gases (2DEGs) and terahertz (THz) free-electron lasers in thepresence of quantizing magnetic fields. It is found both experimentally and theoreticallythat when an intense THz field and a quantizing magnetic field are applied simultaneouslyto a GaAs-based 2DEG in the Faraday geometry, a strong cyclotron resonance (CR) effecton top of the magnetophonon resonances can be observed by transport measurements atrelatively high temperatures. With increasing radiation intensity and/or decreasingtemperature, the peaks of the CR are broadened and split due to magnetophoton–phononscattering.