Electrical and optical properties of vanadium-related centers in silicon

Vanadium-doped silicon was investigated using junction space-charge techniques. Three energy levels were observed at ${\mathit{E}}_{\mathit{c}}$-0.21 eV (A level), ${\mathit{E}}_{\mathit{c}}$-0.48 eV (B level), and ${\mathit{E}}_{\mathit{v}}$+0.36 eV (C level). The enthalpies of electron capture are 4 and 16 meV for the A and B levels, respectively. The corresponding enthalpy of holes is 88 meV for the C level. It is believed that electron capture into the A and B levels is due to a cascade process. Changes in the Gibbs free energy as a function of temperature were calculated for all three levels. The good agreement of the Gibbs free energies with the optical threshold energies suggests negligible lattice relaxations. A structure in the low-energy part of the spectral distribution of the electron photoionization cross sections of the B level is assumed to be due to excited states and shown to be in good agreement with effective-mass theory.