Advanced Knowledge for Impurity Motion of Oxygen in Silicon and its Application to Defect-State Analysis

Abstract

AbstractWe review our two models for the impurity excitation of the oxygen in silicon. The first model aims to explain the energies and intensities of the infrared absorption lines. The coupled excitation is formulated for the first time under the D3d symmetry. Taking into account the lowenergy excitation of the oxygen, the A2u local mode, and the anharmonic coupling between them, we quantitatively describe the absorption lines in the 30-, 1100-, and 1200-cm−1 bands, including those of the 18O isotope. We next take into account the A1g local mode, the Eu resonant mode, and the couplings between the excitation elements. This enables us to qualitatively explain the origin and characteristic aspects of other absorptions, e.g., the 500- and 1700-cm−1 bands. The second model is a simplification of the first one with the coupling to the band (extended) phonons included. The model describes the strong temperature dependence of the line widths observed for both of the phonon-resonant 30-cm−1 band and the phonon-off-resonant 1100-cm−1 band. The life-time limiting process causing the finite line-widths is shown to be the one-phonon transitions in the energy-level ladders of the low-energy excitation each belonging to the ground and the first excited states of the A2u local mode. The vibrational excitations of the similar impurity systems in Si, Ge, Ge xSi1−x crystals are analyzed.