The spatial separation of electron-hole pairs in Si/Ge heterostructures

• Main Authors: Lysenko, V.S., Kondratenko, S.V., Melnichuk, Ye.Ye., Terebinska, M.I., Tkachuk, O.I., Kozyrev, Yu.N., Lobanov, V.V.
• Format: Article
• Language: English
• Published: Інститут хімії поверхні ім. О.О. Чуйка НАН України 2015
• Series: Поверхность
• Subjects: Наноматериалы и нанотехнологии
• Online Access: http://dspace.nbuv.gov.ua/handle/123456789/148495

Photogeneration and transport of nonequilibrium charge carriers, and the determination of photoresponce mechanisms in semiconductor SiGe/Si and SiGe/SiO₂/p-Si heterostructures with nanoisland were investigated. The structures were grown by molecular beam epitaxy technique. The work generalizes the results of studies of morphological, structural, optical and electrical properties of heterostructures with nanoscale objects – quantum dots and quantum wells. 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 in nanoislands Si1-xGex is determined by interband and intraband transitions involving localized states of the valence band of the Ge nanoscale objects. The effects of long-decay photoconductivity and optical quenching of conductivity in SiGe/SiO₂/p-Si heterostructures with SiGe nanoclusters was found to be caused by variations of the electrostatic potential in the near-suraface region of p-Si substrate and optically-induced spatial redistribution of trapped positive charges between SiO₂/Si interface levels and localized states of Ge nanoislads. Adsorption complexes of germanium on the reconstructed Si(001)(4×2) surface have been simulated by the Si₉₆Ge₂Н₈₄ cluster. For Ge atoms located on the surface layer of the latter, DFT calculations (B3LYP, 6-31G**) of their 3d semicore-level energies have shown a clear-cut correlation between the chemical shifts and mutual arrangement of Ge atoms.