Measurements of the effective surface recombination velocity at Si surfaces which were passivated by plasma-enhanced chemical vapor deposited nitride films were performed on monocrystalline Si wafers by using a microwave-detected photoconductance decay method. In order to simulate the measured dependence of the surface recombination velocity on the bulk injection level, an extended Shockley-Read-Hall formalism was used. The simulation input parameters included the energy-dependent interface state densities and the capture cross-sections of interface defects. The energy-dependent properties of the interface defects were determined experimentally by means of small-pulse deep-level transient spectroscopy. These measurements revealed the existence of 3 deep Si dangling-bond defects at the Si/SiNx interface. These had similar interface state densities but very different capture cross-sections and recombination rates. Another defect was found very close (less than 0.1eV) to the edge of the Si conduction band. This defect was identified as being the K+ center. In order to obtain good agreement between measured and calculated surface recombination velocities, an order-of-magnitude reduction in insulator charge density was found to be necessary. This was attributed to the capture of electrons from the Si conduction band, and into K+ centers. A comparison of Si/SiNx interfaces which had been prepared by using different techniques showed that the predominant interface defect was produced by ion bombardment during SiNx deposition.

Carrier recombination at silicon/silicon-nitride interfaces fabricated by plasma-enhanced chemical vapor deposition J.Schmidt, A.G.Aberle: Journal of Applied Physics, 1999, 85[7], 3626-33