Exciton dynamics in GaAs/AlxGa1-xAs quantum wells
نویسندگان
چکیده
Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The changes induced in the optical absorption spectrum of a GaAs/Al x Ga 1Ϫx As multiple quantum well due to a photoexcited carrier distribution are reexamined. We use a femtosecond pump-probe technique to excite excitons and free electron-hole pairs. We find that for densities up to 10 11 cm Ϫ2 the saturation of exciton absorption is caused both by a reduction of the oscillator strength and by a broadening of the exciton resonance , which exhibit quite different temporal evolutions. The restoring of the initial value of the reduced oscillator strength is determined by the free-carrier lifetime, which we have measured to be 65 ps, whereas the temporal evolution of the broadening is due to the exciton-exciton interaction and determined by the exciton lifetime, which is found to be 410 ps. We have measured the oscillator strength saturation densities and shown that at low temperature the influence of free electron-hole pairs on the exciton oscillator strength is twice as effective as the influence of other excitons. ͓S0163-1829͑99͒11011-7͔
منابع مشابه
Nonparabolic band effects in GaAs/AlxGa1−xAs quantum dots and ultrathin quantum wells
We have investigated the optical properties of unstrained GaAs/AlxGa1−xAs quantum dot/well systems with the aim of studying the influence of confinement on the effective exciton mass, as determined from the photoluminescence line shift in high magnetic fields 50 T . The effective exciton mass is found to be more than twice the value for bulk GaAs. We attribute this to an enhanced nonparabolicit...
متن کاملDynamics of exciton transfer between the bound and the continuum states in GaAs-AlxGa1-xAs multiple quantum wells.
Experimentally observed two-exponential decay of excitonic transitions in GaAs-Al Gal — As multiple quantum wells has been successfully interpreted in terms of the exciton transfer between the continuum (free carriers) and the bound states. The calculation results obtained from this exciton-transfer model are in excellent agreement with experimental observations. The rates of the exciton transf...
متن کاملNegatively and positively charged excitons in GaAs/AlxGa1-xAs quantum wells.
We report the observation of the positively charged exciton and of the triplet state of the negatively charged exciton in modulation doped GaAs quantum wells. Applying a gate voltage at high magnetic fields we find that the photoluminescence line of the two-dimensional electron gas smoothly transforms into a negatively charged exciton and not into a neutral exciton. The Zeeman splitting of this...
متن کاملEffect of charge-carrier screening on the exciton binding energy in GaAs/AlxGa1-xAs quantum wells.
Exciton binding energies of heavyand light-hole excitons affected by charge-carrier screening in GaAs-Al„Ga& As quantum wells are calculated by the variational-perturbation method. The exciton binding energies are found to decrease rapidly when the screening length is less than 30az (effective exciton Bohr radius). This screening length corresponds to a carrier density of 7.0X 10"/cm at T=10 K....
متن کاملElectronic structures of GaAs/AlxGa1-xAs quantum double rings
In the framework of effective mass envelope function theory, the electronic structures of GaAs/AlxGa1-xAs quantum double rings (QDRs) are studied. Our model can be used to calculate the electronic structures of quantum wells, wires, dots, and the single ring. In calculations, the effects due to the different effective masses of electrons and holes in GaAs and AlxGa1-xAs and the valence band mix...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2016