Structure Analysis of Point-Defect-Aggregates in Semiconductors by Means of Crystallographic Techniques

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Point defects in a semiconducting material are introduced during crystal growth, heat treatment, electron irradiation and ion-implantation. It is well known that they gave a considerable chance to aggregate at elevated temperatures. Atomic structures of several aggregates have remained uncertain, and this fact has caused unnecessary confusion. In the present research, atomic structures of the aggregates have been analyzed by means of transmission electron diffraction and transmission electron microscopy. Since the atoms which constitute a covalent material have a strong tendency to form covalent bonds even in a defect region, it is expected that the atomic structure of aggregates has a kind of order. This is the reason of the advantage of transmission electron diffraction and electron microscopic techniques, which are very convenient means to analyze small particles of a periodic structure which are embedded in the matrix crystal. The results of our analysis are summarized as follows.1 … More . Defect on {113} in Si and GeA proposed atomic model shows that interstitial Si atoms aggregate on {113} and form a reconstructed structure in the interior of a Si crystal. The model is characterized by 5-6-7-and 8-membered atomic rings and has no dangling bond in the {110} projection. The 6-membered rings constitute tiny rods of the hexagonal structure, and the 8-membered rings are related to the {113} surface structure. It has been confirmed based on an energy calculation that the energy per self interstitial atom in the reconstructed structure is distinctively smaller than that estimated for an isolated interstitial atom.2. Planar defects in a Si-doped GaAs crystalSmall precipitates of triangular shape are observed in a Si-doped GaAs crystal. Transmission electron microscopic study has indicated that the two {111} crystallographic net planes of Si are inserted between the two existing {111} net planes in a GaAs crystal.Furthermore, we have proposed a new atomic model for a hydrogen-induced platelet in Si based on the precise analysis of high-resolution electron microscopic images.In conclusion, the crystallographic techniques such as electron diffraction and microscopy are very useful in analyzing atomic structures of point-defect-aggregates in semiconducting materials. Less