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HL: Fachverband Halbleiterphysik

HL 40: Impurities / Amorphous Semiconductors

HL 40.4: Vortrag

Dienstag, 27. März 2012, 12:15–12:30, EW 015

Defects in amorphous silicon nitrides: Si₃N₄-Si₃N_x — •Leif Eric Hintzsche, Georg Kresse, Martijn Marsmann, Gerald Jordan, Changming Fang, and Thomas Watts — Computational Materials Physics, University of Vienna, Sensengasse 8/12, 1090 Vienna, Austria

Amorphous silicon nitride is widely used for memory and photovoltaic devices. In solar cells, it serves as a passivation and antireflection layer. In most cases, the silicon nitride layers are not stoichiometric and contain significant amounts of hydrogen. Currently, it is not well understood what distinguishes a good passivation layer that minimizes reflection losses from a bad passivation layer. To gain a more detailed atomic scale understanding, we present a careful study of the electronic properties of stoichiometric and non-stoichiometric silicon nitrides in the range of Si₃N₅-Si₃N₃. For each stoichiometry, several structural models are created containing typically 100 Si atoms. The evolution of the band gap, participation ratio, as well as the geometric and electronic defects states are analysed in detail. For the preparation of the structures, simulated annealing combined with standard density functional theory is applied, whereas the Heyd-Scuseria-Ernzerhof hybrid functional is used to analyse the electronic properties of the final structures.