Dissertations

Kondratenko S.V.

27.06.2013

Photogeneration and recombination of non-equilibrium charge carriers in semiconductor nanoheterostructures Si(1-x)Gex/Si and InxGa(1-x)As/GaAs.
01.04.05 – optics, laser physics
Doctor of physical and mathematical sciences

The thesis presents the study of the photogeneration and recombination of nonequilibrium charge carriers, and the determination of photoconductivity mechanisms in semiconductor SiGe/Si and InGaAs/GaAs heterostructures with the quantum-sized objects. The work generalizes the results of studies of morphological, structural, optical and electrical properties of semiconductor nanoheterostructures. It is shown that the photoconductivity of nanoheterostructures SiGe/Si in the infrared range depending on the component composition, size and magnitude of the mechanical stresses nanoislands Si(1-x)Gex is determined by interband and intraband transitions involving localized states of valence band of the nanoislands. The effects of residual conductivity and optical quenching of conductivity in SiGe/SiO2/p-Si heterostructures with SiGe nanoclusters first found to be caused by variations of the electrostatic potential in p-Si and optical charge and SiO2/Si interface state nanoclusters SiGe. It was shown that the positive charge trapped by SiGe nanoislands has strong effect on the thermally activated exchange of holes between states of the wetting layer and nanoislands and determines in general the conductivity of p-i-n Si/Ge heterostructure at low temperatures. The electron spectrum of interface states in GaAs vicinity of InGaAs/GaAs heterostructures with quantum dots and quantum wires was determined. Besides, these states are the centers of electron trapping and determine high photosensitivity and the long-time kinetics of photoconductivity. The optical quenching of photoconductivity in multilayer InGaAs/GaAs nanoheterostructures due to the optical re-charge of EL2 centers and variations of the band gap of GaAs spacer layers was first shown.
Keywords: photovoltaic properties, nanoislands, heterostructures, quantum dots, quantum size effects, photoconductivity, photoluminescence, optical quenching conductivity.

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