Transient photocurrent study of the dangling bond centre in undoped amorphous silicon

Abstract

The spectra of all four cross-sections for optical transitions associated with a correlated dangling bond centre in undoped amorphous silicon have been derived by combining transient and modulated photocurrent measurements. Analysis of the spectral shape of these cross-sections yields the energies of transitions between extended band states and the dangling bond centres with single and double occupancy, providing a unique energy placement of the dangling bond states. The results show that the singly and doubly occupied dangling bond states are located about 0.88 and 0.62 eV below the conduction-band edge, respectively, and the effective correlation energy is around 0.26 eV. Lattice relaxation energies are found to be between 0.09 and 0.13 eV. This implies a negligible role for lattice relaxation in the dangling bond transitions.