EFFECTS OF EXTERNAL AND INTERNAL ELECTRIC FIELDS ON THE BORON ACCEPTOR STATES IN SILICON

Abstract

Effects of various electrical perturbations on the boron acceptor states in silicon were studied using low-temperature absorption-line measurements.A uniform external electric field was applied to compensated boron-doped silicon and the "Stark effect" on the boron acceptor absorption lines was observed. The Stark shifts of the excited states were quadratic in the applied field. The Stark broadening of the acceptor absorption lines was attributed to an unresolved partial removal of degeneracy of the excited states. The internal Coulomb fields of ionized impurities also perturb neutral acceptor transitions, resulting in (a) "ionized impurity broadening" of the absorption lines by the screened Coulomb fields of thermally ionized impurities in uncompensated Si(B) silicon at T > 50 °K and (b) "compensation effects" on the absorption lines by the unscreened Coulomb fields of compensationally ionized impurities in Si(B, P) silicon at 4 °K. Observations of these two internal Coulomb held effects are related to the external-field Stark effects. The theories of ionized impurity broadening are discussed briefly and the observed properties of a new absorption line due to compensation are reported.