Dynamics and control of nonradiative excitons - free carriers mixture in GaAs/AlGaAs quantum wells
A. S. Kurdyubov, A. V. Trifonov, B. F. Gribakin, P. S. Grigoryev, I. Ya. Gerlovin, A. V. Mikhailov, I. V. Ignatiev, Yu. P. Efimov, S. A. Eliseev, V. A. Lovtcius… 展开作者
A. S. Kurdyubov, A. V. Trifonov, B. F. Gribakin, P. S. Grigoryev, I. Ya. Gerlovin, A. V. Mikhailov, I. V. Ignatiev, Yu. P. Efimov, S. A. Eliseev, V. A. Lovtcius, M. Aßmann, A. V. Kavokin
Dynamics of nonradiative excitons with large in-plane wave vectors forming a so-called reservoir is experimentally studied in a high-quality semiconductor structure containing a 14-nm shallow GaAs/Al$_{0.03}$Ga$_{0.97}$As quantum well by means of the non-degenerate pump-probe spectroscopy. The exciton dynamics is visualized via the dynamic broadening of the heavy-hole and light-hole exciton resonances caused by the exciton-exciton scattering. Under the non-resonant excitation free carriers are optically generated. In this regime the exciton dynamics is strongly affected by the exciton-carrier scattering. In particular, if the carriers of one sign are prevailing, they efficiently deplete the reservoir of the nonradiative excitons inducing their scattering into the light cone. A simple model of the exciton dynamics is developed, which considers the energy relaxation of photocreated electrons and holes, their coupling into excitons, and exciton scattering into the light cone. The model well reproduces the exciton dynamics observed experimentally both at the resonant and nonresonant excitation. Moreover, it correctly describes the profiles of the photoluminescence pulses studied experimentally. The efficient exciton-electron interaction is further experimentally verified by the control of the exciton density in the reservoir when an additional excitation creates electrons depleting the reservoir.
Quantum corrections to the conductivity and Hall coefficient of a 2D electron gas in a dirty AlGaAs/GaAs/AlGaAs quantum well: transition from diffusive to ballistic regime
本文报道了AlGaAs/GaAs/AlGaAs量子阱中低迁移率、高密度二维电子气在宽温度范围（1.5 K - 110 K）内纵向电导率和霍尔系数的量子修正实验研究。这个温度范围涵盖了我们的样品的扩散和弹道相互作用制度。因此，可以研究纵向电导率和霍尔效应的交叉区域。
The effect of spin-orbit interaction was studied in a high-quality $p$-AlGaAs/GaAs/AlGaAs structure with a square quantum well using acoustic methods. The structure grown on a GaAs (100) substrate was symmetrically doped with carbon on both sides of the quantum well. Shubnikov-de Haas-type oscillations of the ac conductance of two-dimensional holes were measured. At a low magnetic field $B <$2 T conductance oscillations undergo beating induced by a spin-orbit interaction. Analysis of the beating character made it possible to separate the conductance contributions from the two heavy holes subba…
Quantum corrections to the conductivity and Hall coefficient of a two-dimensional electron gas in a dirty AlGaAs/GaAs/AlGaAs quantum well: from the diffusive to the ballistic regime
It is experimentally shown that the pressure applied along the twofold symmetry axis of a heterostructure with a wide GaAs/AlGaAs quantum well leads to considerable modification of the polariton reflectance spectra. This effect is treated as the stress-induced decrease of the heavy-hole exciton mass. Theoretical modeling of the effect supports this assumption. The 5\%-decrease of the exciton mass is obtained at pressure P=0.23 GPa.
Temperature and Electron Density Dependence of Spin Relaxation in GaAs/AlGaAs Quantum Well
利用时间分辨克尔旋转技术研究了具有不同结构对称性的GaAs/AlGaAs量子阱的自旋动力学随温度和载流子密度的变化。与非对称GaAs量子阱相比，对称GaAs量子阱的自旋弛豫时间要长得多，表明Rashba自旋轨道耦合对自旋弛豫有很强的影响. D 'yakonov-Perel'（DP）机制是GaAs/AlGaAs量子阱自旋弛豫的主要机制。自旋弛豫时间表现出非单调依赖于温度和光激发载流子密度的行为，揭示了电子-电子库仑散射的非单调温度和密度依赖性的重要作用。我们的实验观察表明，与最近发展的自旋弛豫理论的基础上微观动力学自旋布洛赫方程的方法很好的协议。
We study phonon emission in a GaAs/AlGaAs double quantum dot by monitoring the tunneling of a single electron between the two dots. We prepare the system such that a known amount of energy is emitted in the transition process. The energy is converted into lattice vibrations and the resulting tunneling rate depends strongly on the phonon scattering and its effective phonon spectral density. We are able to fit the measured transition rates and see imprints of interference of phonons with themselves causing oscillations in the transition rates.
We study hydrodynamic and ballistic transport regimes through nonlocal resistance measurements and high-resolution kinetic simulations in a mesoscopic structure on a high-mobility two-dimensional electron system in a GaAs/AlGaAs heterostructure. We evince the existence of collective transport phenomena in both regimes and demonstrate that negative nonlocal resistances and current vortices are not exclusive to only the hydrodynamic regime. The combined experiments and simulations highlight the importance of device design, measurement schemes and one-to-one modeling of experimental devices to de…
We report on nonlinear transport measurements in a two-dimensional electron gas hosted in GaAs/AlGaAs heterostructures. Upon application of direct current, the low-temperature differential resistivity acquires a positive correction, which exhibits a pronounced maximum followed by a plateau. With increasing temperature, the nonlinearity diminishes and disappears. These observations can be understood in terms of a crossover from the Bloch-Grüneisen regime to the quasielastic scattering regime as the electrons are heated by direct current. Calculations considering the interaction of electrons wit…
利用一种新型的碳掺杂源，在GaAs/AlGaAs异质结中的对称量子阱结构中制备了二维空穴气。在密度为2.3 x 10^11 cm^-2时，GaAs（001）衬底上的低温空穴迁移率高达1.2 x 10^6 cm ^2/Vs。与电子系统相比，空穴迁移率敏感地依赖于量子阱宽度和间隔层厚度的变化。特别地，量子阱宽度从15 nm的最佳值增加到18 nm伴随着空穴迁移率降低35%。超高迁移率电子系统的质量不受所采用的碳掺杂源的影响。
We present measurements of Coulomb drag in an ambipolar GaAs/AlGaAs double quantum well structure that can be configured as both an electron-hole bilayer and a hole-hole bilayer, with an insulating barrier of only 10 nm between the two quantum wells. The Coulomb drag resistivity is a direct measure of the strength of the interlayer particle-particle interactions. We explore the strongly interacting regime of low carrier densities (2D interaction parameter $r_s$ up to 14). Our ambipolar device design allows comparison between the effects of the attractive electron-hole and repulsive hole-hole i…
We present measurements of low frequency charge noise and conductance drift in modulation doped GaAs/AlGaAs heterostructures grown by molecular beam epitaxy in which the silicon doping density has been varied from $2.4\times 10^{18} cm^{-3}$ (critically doped) to $6.0\times 10^{18} cm^{-3}$ (overdoped). Quantum point contacts were used to detect charge fluctuations. A clear reduction of both short time scale telegraphic noise and long time scale conductance drift with decreased doping density was observed. These measurements indicate that the {\it neutral} doping region plays a significant rol…
The paper reports optical orientation experiments performed in the narrow GaAs/AlGaAs quantum wells doped with Mn. We experimentally demonstrate a control over the spin polarization by means of the optical orientation via the impurity-to-band excitation and observe a sign inversion of the luminescence polarization depending on the pump power. The g factor of a hole localized on the Mn acceptor in the quantum well was also found to be considerably modified from its bulk value due to the quantum confinement effect. This finding shows the importance of the local environment on magnetic properties…
We report the results of a combined microwave polarization-dependence and power-dependence study of the microwave-radiation-induced magnetoresistance oscillations in high mobility GaAs/AlGaAs heterostructure devices at liquid helium temperatures. The diagonal resistance was measured with the magnetic field fixed at the extrema of the radiation-induced magnetoresistance oscillations, as the microwave power was varied at a number of microwave polarization angles. The results indicate a nonlinear relation between the oscillatory peak or valley magnetoresistance and the microwave power, as well as…
