Observation of multiple defect states at silicon–silicon nitride interfaces fabricated by low-frequency plasma-enhanced chemical vapor deposition

Silicon nitride films are deposited onto monocrystalline p- and n-type silicon wafers by low-frequency plasma-enhanced chemical vapor deposition. Using small-pulse deep-level transient spectroscopy, three different types of defects are identified at the silicon–silicon nitride interface. All defects are located in the lower half of the silicon band gap and show a very broad Gaussian-like distribution of the state density. For all three defects, the capture cross sections for electrons, ${\sigma }_n,$ and holes, ${\sigma }_p,$ decrease strongly towards the conduction and valence band edge, respectively, while the capture cross-section ratio ${\sigma }_n{\mathrm{/\sigma }}_p$ at midgap, and hence the resulting recombination rate, is very different for each defect type.