Фотолюминесценция с временным разрешением в гетероструктурах с квантовыми ямами InGaAs:Cr/GaAs

We present the results of time-resolved photoluminescence measurements carried out for semiconductor heterostructures containing two non-interacting quantum wells in the GaAs matrix: an undoped InGaAs quantum well and a quantum well uniformly doped with chromium atoms (InGaAs : Cr). It has been shown that the introduction of Cr significantly affects the recombination lifetime of carriers in quantum wells. The change in the intensity of photoluminescence, starting from the moment of excitation, is not described by a monoexponential decay function, which is explained by a change in the built-in electric field of the surface barrier in quantum wells due to screening by photoexcited carriers.

THz Superradiance from a GaAs: ErAs Quantum Dot Array at Room Temperature

We report that an ErAs quantum-dot array in a GaAs matrix under 1550 nm pulsed excitation produces cooperative spontaneous emission—Dicke superradiance—in the terahertz frequency region at room temperature. Two key points pertain to the experimental evidence: (i) the pulsed THz emission power is much greater than the continuous wave (CW) photomixing power; and (ii) the ultrafast time-domain waveform displays ringing cycles. A record of ~117 μW pulsed THz power was obtained, with a 1550 nm-to-THz power conversion efficiency of ~0.2%.

Исследование спонтанной эмиссии в брэгговских монослойных квантовых ямах InAs

The time-resolved photoluminescence of a Bragg structure formed by InAs single-layer quantum wells in a GaAs matrix is investigated experimentally. The comparison of photoluminescence spectra recorded from the edge and the surface of the sample indicates that Bragg ordering of the quantum wells leads to substantial modification of the spectra, in particular, to the appearance of additional modes. The spectrum recorded at the edge of the sample features a single line corresponding to the exciton ground state. In the spectrum recorded at the surface, an additional line whose frequency and propagation angle correspond to the Bragg condition for quantum wells, appears at high excitation levels. The calculation of the modal Purcell factor explains the fact that spontaneous emission is enhanced only for specific propagation angles and frequencies, rather than for all angles and frequencies satisfying the Bragg condition.

Электрополевое поведение резонансных особенностей в туннельной составляющей фототока в гетероструктурах InAs(QD)/GaAs

The electric-field behavior of resonance features of the photoelectric characteristics of InAs/GaAs heterostructures is investigated. The emission of carriers excited by light from InAs quantum dots into the GaAs matrix is ​​discussed. It is shown that at the temperature of liquid nitrogen the photocurrent in a strong transverse electric field is only determined by the effect of electron tunneling through a barrier formed at the quantum-dot interfaces. Comparison of the experimental curves with the results obtained using a quasiclassical expression for the tunneling-current component and subsequent analysis of the potential structure made it possible to refine the parameters of the heterostructure under study. The contribution of the resonance component caused by possible electron tunneling through the barrier with the participation of the local defect states to the total tunneling current is analyzed. The influence of the level of excitation of the system on the photocurrent flowing through the InAs/GaAs heterojunction is theoretically studied.