Influence of laser crystallization on hydrogen bonding in poly‐Si

Abstract

We investigate the influence of the hydrogen content in the amorphous starting material on hydrogen bonding and defect passivation in laser crystallized poly‐Si using electron‐spin‐resonance and hydrogen effusion measurements. After laser dehydrogenation and crystallization the specimens contain a residual H concentration of 8×1021 cm–3 to 1.5×1022 cm–3. During a vacuum anneal at least 1.5×1021 cm–3 H atoms are mobile in the lattice, however, only about 3.7×1018 cm–3 H atoms passivate Si dangling‐bonds. Our results show that the annealing treatment can cause the vast majority of H atoms to accumulate in H stabilized platelets. Since defect passivation preferentially occurs at grain boundaries and platelet nucleation and growth is confined to the interior of single crystal grains, H equilibration is governed by two spatially separated processes. Moreover, our data demonstrate that the hydrogen density‐of‐states distribution derived from H effusion data is dynamic and changes in response to experimental parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)