Resonant interactions of optical phonons with acceptor continuum states in silicon

Abstract

We have performed and analyzed optical-absorption experiments which provide clear evidence of Breit-Wigner-Fano resonant interactions between the electronic continuum states of acceptors and localized excitations involving optical phonons in silicon. For boron, the 519-${\mathrm{cm}}^{-1\mathrm{}}$ zone-center phonon lies within the region of excitation to the continuum of the $p_{\frac{3}{2}}$ valence band, leading to an antiresonance at that wave number. In addition, antiresonances are observed in silicon doped with boron at 764 ${\mathrm{cm}}^{-1\mathrm{}}$, aluminum at 962 ${\mathrm{cm}}^{-1\mathrm{}}$, and gallium at 989 ${\mathrm{cm}}^{-1\mathrm{}}$. These numbers correspond to the one-phonon sidebands of the bound-to-bound $1S_{\frac{3}{2}}\to 2P_{\frac{3}{2}}$ impurity excitations, which lie within the region of excitation to the continuum of the $p_{\frac{1}{2}}$ valence band. Fano's theory is used to analyze these results.