Correlation of charge transport to local atomic strain in Si-rich silicon nitride thin films

Charge transport in Si-rich silicon nitride thin films is investigated. Over a composition range from Si3N4 to SiN0.54 the field dependent current density is observed to increase by as much as seven orders of magnitude, the residual Si–N bond strain decreases from 0.006 to −0.0026 and the Poole–Frenkel barrier height, ΦB, decreases from 1.08 to 0.55 eV. A direct correlation between ΦB and the local atomic strain is observed. It is concluded that reductions in ΦB are a manifestation of compositionally induced strain relief at the molecular level. Reductions in ΦB result in increased Poole–Frenkel emission rates and consequently higher conductivities in Si-rich films.