An ab initio local density functional cluster method, AIMPRO, is used to examine oxygen related point defects in silicon, and H-related complexes in III-V semiconductors, notably InP.
Models are proposed for three different types of shallow thermal donor in silicon, NiO2i, (CH)iO4i and AlsO4i. This includes a new mechanism for converting otherwise deep level defects into shallow donor level centres, through electrostatic compression via neighbouring oxygen atoms. A reconstruction mechanism is also found whereby (CH)iO4i can transform into a deep state defect.
Several thermal donor models are examined, and a centre consisting of a `di-y-lid', O4i, is shown to account for most of the observed experimental properties. Higher order thermal donor formation is discussed, as well as the role of hydrogen and silicon self-interstitials in thermal donor behaviour.
Rapid oxygen diffusion is examined in the context of the oxygen dimer, O2i. A puckered dimer structure is shown to be stable with 16O modes in good agreement with experiment. A low energy migration path for dimer diffusion is determined. The role of the dimer in creating other oxygen-based point defects in silicon is discussed.
Oxygen complexes with nitrogen are also modelled, and the most common N/O defect is shown to be N2iOi, consisting of bond centred oxygen neighbouring an interstitial nitrogen square. A NiOi complex is also identified and correlated with experimental data. Various vacancy-oxygen complexes are studied and their anomalous formation discussed. The structure VO2 is unambiguously assigned to experimental infra-red absorption at 889 cm-1.
Finally the interaction between hydrogen, Group-II elements and vacancies in III-V materials is examined, particularly InP. VH4 in InP is shown to be a single shallow donor, responsible for Fe charge compensation observed in InP:Fe-H. Trends in structure with varying Group-II element and III-V material are examined.