Multiphonon trap ionization transport in nonstoichiometric SiN _x

It is generally accepted that the charge transport in dielectrics is governed by coulombic trap ionization due to a barrier lowering in high electric fields (Frenkel effect). In this paper, the charge transport mechanism in Si₃N₄ and nonstoichiometric silicon rich SiN_x is experimentally studied and quantitatively analyzed with five theoretical models: Frenkel model of Coulomb traps ionization, Hill-Adachi model of overlapping Coulomb traps, Shklovskii-Efros percolation model, Makram-Ebeid and Lannoo model of multiphonon isolated traps ionization and Nasyrov-Gritsenko model of phonon-assisted electron tunneling between nearby traps. It is shown that the charge transport in Si₃N₄ and SiN_x is qualitatively described by Frenkel effect, but Frenkel effect predicts an enormously low attempt to escape factor value. The charge transport at traps energies W _t = 1.6 eV and W _opt = 3.2 eV in Si₃N₄ and SiN_x can be described by an increase in traps concentration in the framework of Makram-Ebeid and Lannoo model and Nasyrov-Gritsenko model. The Makram-Ebeid and Lannoo model quantitatively describes the charge transport in Si₃N₄ and SiN_x with low silicon enrichment. The charge transport in nonstoichiometric SiN_x with high silicon enrichment is well explained by Nasyrov-Gritsenko model.