Interaction and dephasing of center-of-mass quantized excitons in wideZnSe/Zn0.94

Abstract

. Interaction and dephasing of center-of-mass quantized excitons in wide ZnSe/Zn0.94Mg0.06Se quantum wells. Physical Review B, 57(3), 1791-1796. DOI: 10.1103/PhysRevB.57.1791 Interaction and dephasing of center-of-mass quantized excitons in wide ZnSe/Zn 0. We investigate the interaction and dephasing of the excitons in wide ZnSe/Zn 0.94 Mg 0.06 Se quantum wells by spectrally resolved, femtosecond four-wave mixing ͑FWM͒. Polarization-dependent measurements indicate that excitation-induced dephasing is the dominant FWM process. The biexcitons of the center-of-mass quantized heavy and light hole excitons are observed, showing binding energies of 3.5 meV. We determine the exciton scattering cross sections with incoherent and coherent excitons. The coherent cross section is found to be larger than the incoherent cross section, which is attributed to a stronger Pauli repulsion for coherent excitons. The exciton interaction rates with acoustic and optical phonons are deduced by their temperature dependencies. The acoustic-phonon scattering is found to be strongly reduced in the investigated wide wells due to the reduced accessible phonon wave vector. ͓S0163-1829͑98͒00803-0͔

Ultrafast Phenomena in II-VI Semiconductors

“…We find an exciton-exciton interaction parameter γxx of about 4 and 1.1 depending on the negative delay time of the prepump. These interaction parameters are quite similar to the ones found in ZnSe/ZnSSe QWs [1], in wide ZnSe/ZnMgSe QWs [11], in CdTe/CdZnTe QWs [12], and in GaAs/AlGaAs QWs [10]. But, it is a striking result that the interaction parameter in the case of coherent exciton interaction (τ31 = 0 ps) is nearly four times larger than the one for a dephased background population (τ31 = -5 ps).…”

“…On the timescale of the dephasing of the macroscopic polariZation related to the background exciton population, Γ hom drops by about 30% to reach a value close to the one without prepump. We interpret this finding as a clear indication that the excitonic interactions are far more efficient between coherent excitons than between incoherent ones [11].…”

Mixed biexcitons in single quantum wells

“…2͑a͒ for ͑↑→͒ excitation. These oscillations are caused by the interference of LFE and BIF induced polarizations, 7 and are not present in the XX h trace. From the oscillation period we deduce ⌬ h ϭ4.7 meV, in good agreement with ⌬ h ϭ4.8 meV obtained from the FWM spectra.…”

“…1-4 Since a biexciton can be directly excited by two-photon excitation, the nonlinear optical technique of degenerate four-wave mixing ͑FWM͒ provides a powerful tool to study coherent biexcitonic phenomena. [4][5][6][7] So far, these studies consider mainly the biexciton formation from two heavy-hole excitons (X h ). Biexcitons involving light-hole excitons (X l ) have been observed, 8 but no distinction between mixed and pure lighthole biexcitons has been made.…”

Exciton dephasing and biexciton binding in CdSe/ZnSe islands

“…These effects are particularly important in II-VI materials because of their large biexciton binding energy, which strongly influences their stimulated emission. Four-wave mixing ͑FWM͒ provides a powerful tool to study the fundamental coherent processes in low-dimensional II-VI semiconductor systems, as already shown in quasitwo-dimensional 19,20 and quasi-one-dimensional structures. 21 In this paper we study CdSe/ZnSe island structures by femtosecond transient FWM.…”