Thermal Generation of Recombination Centers in Silicon

Measurement of minority carrier lifetime versus bulk resistivity in diffused silicon $p-n$ junctions shows that Hall-Shockley-Read statistics are obeyed. Measurement of lifetime versus temperature yields information regarding the depth of the trapping level in the forbidden gap. Lifetime versus temperature data were taken on junctions which were annealed, quenched, and reannealed. A trap level of approximately 0.1 ev above the valence band in both conductivity types of silicon was deduced from the data. The curves indicate that the energy levels remained fixed, regardless of treatment, but the density of centers changed. Ambient temperature lifetimes were measured for $p-n$ junctions which were quenched from a number of different temperatures. This resulted in a Boltzmann-type relationship yielding a formation energy (approximately 1 ev) for the creation of a defect. Mechanisms explaining the observed phenomena are discussed.