Defect re-distribution in amorphous silicon below equilibration temperature

The effect of a Fermi level shift in an intrinsic energy distribution of ga p states of amorphous silicon prepared by glow discharge is investigated wi th the aim of simulating the energy distribution of gap states near the i-n (pi) interface in a p-i-n (n-i-p) device. Therefore we carried out experim ents in which the Fermi level is moved to either the conduction or valence band edge in a 'programmed' intrinsic energy distribution of gap states by subjecting a metal/insulator/amorphous-silicon structure to n-type or p-typ e bias stress, respectively. Its effect on the energy distribution of gap s tates is measured by the charge version of deep level transient spectrometr y. We observe that upon n-type (p-type) bias stress the energy distribution of gap states does not immediately adjust to the applied Fermi level shift , but that first an intermediate distribution is formed with a larger neutr al dangling bond state contribution. In addition, it appears that the negat ively charged dangling bond states are more resistant to p-type stress than the positively charged dangling bond to n-type stress. (C) 2000 Elsevier S cience B.V. All rights reserved.