Excitation spectrum of bismuth donors in silicon

Abstract

The excitation spectrum of the group-V impurity bismuth in silicon has been studied using quantitative uniaxial stress and polarized radiation in conjunction with a high-performance spectrometer and data processing system. This investigation revealed several transitions not reported previously for any donor impurity in silicon, as well as several not reported for this impurity; the energies of all these transitions agree with the calculations of Faulkner. The shear deformation potential constant ${\Xi }_u$ of the $\Delta$-conduction-band minima of silicon has been determined from the effect of uniaxial stress on the excitation spectrum of this impurity; the value of ${\Xi }_u=8.70\mathrm{}\pm 0.18$ eV agrees very well with earlier measurements using other donor spectra. Harris and Prohofsky and Rodriguez and Schultz have developed a theory for the anomalous width of the $2p_0$ transition in this spectrum based on the interpretation by Onton et al. that this is due to a resonant interaction with an optical phonon; the shape of this transition has been carefully compared with the theory using a curve-fitting program in conjunction with the use of uniaxial stress to vary one of the parameters in the theory, the energy of the electronic state. This comparison shows that the theory is qualitatively correct when the energy of the electronic state is larger than the resonance energy, and is inadequate both for the case of electronic energy smaller than the resonance energy and for the case of the interaction with the $2p_{\pm }$ state.