Emission spectra of terahertz quantum cascade laser

We calculated energy levels, wave functions, and energies of radiative transitions in terahertz quantum cascade lasers based on GaAs/Al0.15Ga0.85As heterostructures. Current-voltage characteristics and current dependences of laser radiation intensity were measured, and the maximum operating temperatures reaching 85 K were determined. Radiation spectra of quantum cascade lasers were measured for different temperatures, and the effect of intensity “pumping” from lowfrequency modes to high-frequency modes was found to happen in the case of an increase in the current and time delay of the signal capture, which is explained by heating of the sample during a pulse of the current. Application of the lasers for registration of impurity photoconductivity signals in semiconductor heterostructures was demonstrated

Massless Dirac fermions in III-V semiconductor quantum wells

We report on the clear evidence of massless Dirac fermions in two-dimensional system based on III-V semiconductors. Using a gated Hall bar made on a three-layer InAs/GaSb/InAs quantum well, we restore the Landau levels fan chart by magnetotransport and unequivocally demonstrate a gapless state in our sample. Measurements of cyclotron resonance at different electron concentrations directly indicate a linear band crossing at the $\Gamma$ point of Brillouin zone. Analysis of experimental data within analytical Dirac-like Hamiltonian allows us not only determing velocity $v_F=1.8\cdot10^5$ m/s of massless Dirac fermions but also demonstrating significant non-linear dispersion at high energies.Comment: Main text and Supplemental Materials, 14 pages, 9 figure

Resonance detection of terahertz radiation in submicrometer field-effect GaAs/AlGaAs transistors with two-dimensional electron gas

Resonance detection of terahertz radiation by submicrometer field-effect GaAs/AlGaAs transistors (with the gate length L = 250 nm) with two-dimensional electron gas in the channel has been studied at T = 4.2 K. For these transistors, it is shown for the first time that the maximum of the response (the drain-source photovoltage) shifts with an increasing frequency to the region of higher gate voltages in accordance with the Dyakonov-Shur theory. It is shown that, as temperature is increased to 77 K, the dependence of the photovoltage on the gate voltage becomes nonresonant, which is caused by a decrease in the mobility

Emission spectra of terahertz quantum cascade laser

We calculated energy levels, wave functions, and energies of radiative transitions in terahertz quantum cascade lasers based on GaAs/Al0.15Ga0.85As heterostructures. Current-voltage characteristics and current dependences of laser radiation intensity were measured, and the maximum operating temperatures reaching 85 K were determined. Radiation spectra of quantum cascade lasers were measured for different temperatures, and the effect of intensity “pumping” from lowfrequency modes to high-frequency modes was found to happen in the case of an increase in the current and time delay of the signal capture, which is explained by heating of the sample during a pulse of the current. Application of the lasers for registration of impurity photoconductivity signals in semiconductor heterostructures was demonstrated

Cyclotron resonance in HgTe/CdTe-based heterostructures in high magnetic fields

International audienceCyclotron resonance study of HgTe/CdTe-based quantum wells with both inverted and normal band structures in quantizing magnetic fields was performed. In semimetallic HgTe quantum wells with inverted band structure, a hole cyclotron resonance line was observed for the first time. In the samples with normal band structure, interband transitions were observed with wide line width due to quantum well width fluctuations. In all samples, impurity-related magnetoabsorption lines were revealed. The obtained results were interpreted within the Kane 8*8 model, the valence band offset of CdTe and HgTe, and the Kane parameter EP being adjusted

Magnetooptics of HgTe/CdTe Quantum Wells with Giant Rashba Splitting in Magnetic Fields up to 34 T

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High-field splitting of the cyclotron resonance absorption in strained p-InGaAs/GaAs quantum wells.

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High-field splitting of the cyclotron resonance absorption in strained p-InGaAs/GaAs quantum wells.

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