Properties of amorphous Si-rich silicon nitride prepared by rf-magnetron sputtering

This article investigates the physics underlying held effect passivation of p-type Si surfaces coated with SiNx(:H) of various Si contents. We find a correlation between the effective lifetime of minority carriers in p-type S i passivated with SiNx, on the one hand, and the dark de-conductivity data of corresponding a-SiNx-films with different composition, on the other hand . By increasing the amount of Si in a-SiNx(:H) structures the bandgap decre ases from about 5 to 2 eV. As a result, the dark de-conductivity rises by s everal orders of magnitude. The conductivity prefactors and the activation energies as calculated from the conductivity versus temperature data obey t he Meyer-Neldel relation with an axio-intercept of about 10(-7) (Ohm cm)(-1 ) and a slope of about 35 meV. Thus, Si-rich a-SiNx(:H) films behave like a defect doped n-type semiconductor. The activation energy of the conductanc e in films with the same composition changes with the hydrogen content. A m inimum in the activation energy correlates with a minimum of the surface re combination velocity at the a-SiNx/p-Si interface. We ascribe both effects to a variation of the Fermi level in the films. (C) 2000 Elsevier Science S .A. All rights reserved.