Resonant effects and manyibody interaction in free-carrier semicoductor
plasma
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StatusThe thesis was presented on the 23 September, 2005Approved by NCAA on the 22 December, 2005 Abstract – 2.20 Mb / in romanian |
Keywords
Manybody interaction, semiconductor, multiplasmon transitions, electron-hole pasma, LO-phonon, bound exciton, phonon-plasmons, cathodoluminescence, radiation specta, resonant interaction, quantum wells, multiquantum transitions, correlation effectsSummary
The thesis is devoted to a complex study of resonant effects and manybody interaction in free-carrier semicoductor plasma. The theory of multiplasmon (MP) optical transition in radiative recombination of bound excitons and their two-phonon resonant mechanism with mixed phononplasmon modes are developed, using the cumulant expansion method and fluctuation-dissipation theorem.
The influence of bound exciton interaction with mixed phonon-plasmon modes on bound exciton spectra, energetic levels and spectral lines positions and their relative intensity is studied. It is found that this interaction gets down the energetic level of bound exciton, shifts the spectral lines in the long length region of spectra and effects on their relative intensity.
The luminescence spectra bands shape at different plasma concentration is calculated taking into account the mixed phonon-plasmon modes and MP transitions. It is found that the line -width enhancement, the long wavelength side shoulder apparition at low plasma concentration and the existence of fine MP luminescence bands structure at high plasma concentration are determinated by Coulomb interaction of bound exciton with plasma, and multiplasmon optical transition. The knowledges and mechanisms of bound excitons radiative emission in obtained cathodoluminiscence spectra of ZnSe crystals are systematically examinated. On the base of developed method of luminescence bound excitons spectra bands shape calculation, the information about excitons centers, their concentration and interaction character between elementary crystal excitations is obtained.
It was found that the interaction of bound exciton centres, responsible of Id and Is lines, in case when their energetic levels are separated by the energetic interval equal with the energy of two LO-phonons, has a resonance character and it manifests itself in dublet structure of these lines, observed in experimental cathodoluminiscence spectra of ZnSe crystals. It is demonstrated that the bound excitons emission bands consist of superposition of nonphonon line and their mixed phononplasmon replicas. The mean numbers of emitted phonons and plasmons depend on the centers structure and plasma concentration.
The light absorption and laser gain are calculated in quantum wells with account of strong Coulomb interaction between charge carries and it is shown that multiplasmon transitions smooth the absorption spectra , and shift its switching threshold in the long length region of spectra and created the wavelight gain.
The MP theory of magnetoabsorption of the D- centers in quantum wells is developed with account of their interaction with magneto-plasma under the resonance conditions. The Landau levels splitting causes the thin structure of absorption lines and peaks relative intensity depends of the resonance detuning magnitude.
Generalized Semiconductor Bloch Equation are derived using the fluctuation-dissipation theorem and with account of coherent memory effects and interaction with mixed phonon-plasmon modes.
Numerical calculations of the spontaneous and stimulated emission produced by band-toband multiplasmon recombination of the electron- hole pairs are fulfilled in dependence on the temperature and plasma concentration. It is shown that a multiplasmon light absorption causes the red shift obeying Urbach s rule.
It is demonstrated that developed theoretical models are in accordance with the
corresponding experimental data.
Oficial Reviewers
- Anatolie Casian
doctor habilitat, professor - Mihai Cernei
doctor, associate professor (docent)
Theses
