Charged excitons in GaAs quantum wells

Il Nuovo Cimento D - We implement optical spectroscopy to study charged excitons (trions) in modulation-doped GaAs/AlGaAs quantum wells. We observe for the first time several new trions: the...     

Bound excitons in p-doped GaAs quantum wells

Photoluminescence attributed to excitons bound to neutral impurities has been observed from GaAs quantum wells in Al_xGa_1?xAs-GaAs heterostructures grown by molecular beam epitaxy. The quantum wells were either doped with [Be] ≈ 10¹⁷ cm^-3 or Zn-diffused. At low temperatures both single and multiple quantum wells exhibited this extrinsic luminescence which is ascribed to the radiative recombination of the n=1 ground state heavy hole exciton E_1h bound to a neutral acceptor A^o. The dissociation energy E_D of the A^o-E_1h complex is obtained directly from the measured separation of this extrinsic peak from the intrinsic E_1h free exciton peak. For 46Å wide GaAs wells, E_D=6.5meV and E_D decreases with increasing well width.     

Interwell excitons in GaAs multiple quantum wells and superlattices

Il Nuovo Cimento D - The optical properties of multiple quantum wells in the transition from isolated wells to a superlattice are investigated theoretically and experimentally. For superlattices...     

Influence of acoustic phonons on dephasing of free excitons in quantum wells

A theory of the dephasing rate of quasi-2D free excitons due to acoustic phonon interaction at low exciton densities is presented. Both deformation potential and piezoelectric couplings are considered for the exciton–phonon interaction in quantum wells. Using the derived interaction Hamiltonian obtained recently by us, exciton linewidth and dephasing rate are calculated as a function of the exciton density, exciton temperature, exciton momentum and lattice temperature.     

Radiative recombination of free excitons in GaAs quantum wells

We have measured the radiative lifetime of excitons in GaAs quantum wells under resonant excitation at 10 K using time resolved luminescence spectroscopy with 6 ps time resolution. The luminescence decay has two components: a fast one with a time constant τ₁ (∼ 17 - 40 ps) and a slow one with a time constant τ₂ (∼ 80 - 300 ps). τ₂ is the lifetime of thermalised excitens at 10 K. τ₁ is due to two mechanisms in parallel: the radiative recombination of excitons with k_u < K₀ and the scattering by acoustical phonens into non radiative exciton states (k_u > k₀ and J = 2). The variation with temperature of τ₁ gives the lifetime of the excitons at k = 0, τ₀, which varies between 20 and 50 ps depending on the sample.     

Cretion and annihilation of negatively charged excitons in GaAs quantum wells

Il Nuovo Cimento D - The electroluminescence of p-i-n GaAs double-barrier resonant tunnelling diodes has been investigated for various concentrations of free carriers (either holes or electrons) in...     

GaAs体材料及其量子阱的光学极化退相特性

采用飞秒时间分辨瞬态简并四波混频技术，在室温下测量了GaAs体材料及其量子阱材料GaAs/Al_0.3Ga_0.7As的光学极化超快退相时间，当激光中心波长为785nm，受激载流子浓度为10¹¹cm^-2时，它们的退相时间分别为28fs和46fs.量子阱材料的退相时间比体材料的长，这是由于量子阱中的载流子在垂直于GaAs/AlGaAs界面的运动受到限制，运动呈现二维特性，大大减小了载流子的散射概率.实验中观察到瞬态简并四波混 关键词： 时间分辨简并四波混频 飞秒激光脉冲 退相 密度矩阵     

Condensation of interwell excitons in GaAs/AlGaAs double quantum wells

Experimental observations of the collective behavior of interwell excitons in the binary quantum wells with inclined bands under bias are discussed.     

Localization of negatively charged excitons in GaAs/AlGaAs quantum wells

The localization of negatively charged excitons on isolated charged donors, located in a barrier at various fixed distances L from the heteroboundary, is investigated in isolated GaAs/AlGaAs quantum wells. The energy shift of the cyclotron replica in the emission spectra of a localized excitonic complex is studied as a function of L. It is shown that in undoped samples charged excitons localize on residual donors at distances L>350 Å on account of the formation of D ^? complexes at shorter distances. It is established that a cyclotron replica arises with the recombination of an excited state and not the ground state, as previously thought, of an excitonic complex.