Iliash S. Photoconductivity kinetics and recombination mechanisms of Ge/Si and InGaAs/GaAs barrier heterostructures

The thesis is focused on the complex study of the features of photoexcitation relaxation and determination of photoconductivity mechanisms in barrier structures with nano-sized objects InGaAs and Ge/Si. The research determines the role of nano-objects quantum-dimensional states and energy disordering in the processes of non-equilibrium charge carriers recombination in barrier structures based on the heterojunction of InGaAs/GaAs and Ge/Si. The study shows that the phenomenon of long-term photoconductivity with non-exponential photoexcitation relaxation, found in structures with nano-objects, is explained by spatial distribution of excited electron-hole pair charges by local electric fields and influence of deep traps in nanostructures surrounding. The role of nanostructures in the relaxation of photo-excitation is determined and the phenomenon of increasing the time of photo-EMF and photocurrent attenuation during doping of InAs quantum dots by impurities of a donor type is explained. The thesis shows that the presence of InGaAs quantum dots in the spatial charge of p-i-n diodes leads to the expansion of the spectral range in the IR region (up to 1.2 eV), and their doping with silicon increases the lifetime of nonequilibrium charge carriers by an order of magnitude. Keywords: quantum dots, heterostructures, carrier lifetime, recombination processes, InAs/InGaAs, Ge/Si, nanostructure, semiconductor, photoluminescence, photoconductivity recombination, quantum size state.