Electrical and Optical Properties of Titanium, Vanadium, Molybdenum, and Tungsten Related Defects in Silicon

Abstract

ABSTRACTRecent studies of the deep transition-metal centers Ti, V, Mo and W in silicon are discussed, which have been investigated using junction-space charge techniques. The changes in the Gibbs free energy, enthalpy, and entropy due to electron or hole excitation of these transition metal related levels are presented. The good agreement of the Gibbs free energies with the optical threshold energies of the corresponding photoionization cross sections suggests negligible lattice relaxation. For the Ti-doped samples three energy levels at Ec-0.065 eV, Ec-0.295 eV and Ev+0.255 eV at 80 k were observed. For Mo and W the energy levels are located at Ev+0.298 eV and Ev+0.379 eV, respectively, at 80 K. Three energy levels of the V-related centers exist at Ec-0.207 eV, Ec-0.483 eV and Ev+0.356 eV at 0 K. A structure in the low-energy part of the spectral distribution of the level Ec-0.483 eV is assumed to be due to excited states and shown to be in good agreement with effective-mass theory. Previous assignments of the energy levels should be reconsidered.