High-field backward-wave phonon spectroscopy of Si:In

Abstract

Backward-wave phonon generation in indium-doped silicon has been investigated in the regimes of high input microwave power, high magnetic field, and in the presence of an applied uniaxial stress. The backward-wave phonon-generation process is associated with resonant transitions within the acceptor ground-state quartet. The electric dipole and elastic-field-induced transitions within this quartet are identified with distinct features of the backward-wave spectra. At low microwave power, only strongly allowed transitions are detected. These are associated with indium acceptor sites with little or no static strain splitting of the ground-state quartet. At high microwave powers, two new types of transitions are observed: (i) Weakly allowed but numerous intra-Kramers-doublet transitions dominate at low applied magnetic field, whereas at high applied field inter-Kramers-doublet transitions dominate. Both contributions arise from acceptor sites which experience significant static strain splitting of the quartet. The behavior of these contributions to the spectra as a function of microwave frequency, temperature, and applied uniaxial stress confirms their interpretation and makes possible an estimate of the width of the static strain distribution in these samples. (ii) Superimposed on these broad spectral features are very sharp lines periodic in the applied magnetic field. These sharp lines are not detectable at low power and they vanish on application of uniaxial stress. They are tentatively identified with multiquantum transitions between unidentified, but strongly coupled, energy levels. © 1985 The American Physical Society.