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Volume 93, Issue 5, 01 March 2003
- APPLIED PHYSICS REVIEWS - FOCUSED REVIEW
93(2003); http://dx.doi.org/10.1063/1.1517166View Description Hide Description
Characterization of defect and impurity reactions,dissociation, and migration in semiconductors requires a detailed understanding of the rates and pathways of vibrational energy flow, of the energy transfer channels, and of the coupling mechanisms between local modes and the phonon bath of the host material. Significant progress in reaching this goal has been accomplished in recent landmark studies exploring the excitation and dynamics of vibrational states associated with hydrogen in silicon. The lifetime of the Si–H stretch mode is found to be extremely dependent on the local solid-state structure, ranging from picoseconds for interstitial-like hydrogen, hundreds of picoseconds for hydrogen–vacancy complexes, to several nanoseconds for hydrogen bonded to Si surfaces—over three orders of magnitude variation. Such large variations in lifetime (transition probability) are extraordinarily rare in solid-state science. The level of theoretical investigation into the vibrational lifetime of the Si–H oscillator is less advanced. This state of affairs is partly because of the difficulties in explicitly treating slow relaxation processes in complex systems, and partly because, as suggested by experiment, a highly anharmonic coupling mechanism is apparently responsible for the (multiphonon) relaxation process. Even more importantly, because of the high frequency of the Si–H stretching motion, a quantum mechanical treatment of the Si–H oscillator is required. A combination of Bloch–Redfield theory and molecular dynamics simulation seems promising in describing the relaxation process of the Si–H vibrational modes. It is the aim of this review article to present a comprehensive overview of the recent accomplishments, current understandings, and future directions in this emerging field of time-resolved vibrational spectroscopy of point defects in solids.