Two-Phonon Indirect Transitions and Lattice Scattering in Si

Abstract

The probability of indirect transitions with the emission of two phonons has been calculated. Several of the intensity maxima in the intrinsic low-temperature emission spectrum of Si are explainable in terms of these transitions. Scattering matrix elements obtained from an analysis of the observed emission spectrum indicate that intervalley scattering is the dominant scattering mechanism for electrons in Si, with 0.023-ev and 0.046-ev longitudinal acoustic mode phonons umklapp scattering electrons between valleys on the same and on different crystal axes, respectively. The valleys are approximately 82% of the way from the center to the edge of the Brillouin zone. Optical mode scattering in the valence band is largely responsible for the anomalous temperature dependence of the intrinsic hole mobility.