Redistribution of Recombination Active Defects and Trapping Effects in Multicrystalline Silicon After Wet Thermal Oxidation
In this work we characterised recombination active defects in standard multicrystalline silicon block material by investigating the effect of a wet thermal oxidation step at 800 degC with fast temperature ramps on the effective lifetimes measured by the CDI and QSSPC methods. The average lifetime was significantly decreased by the oxidation step. An increase in the concentration of interstitial iron as well as an increase in the concentration of trapping centres after the oxidation step was observed. A detailed investigation revealed an increase in the recombination activity of grain boundaries. Modeling of measured carrier density profiles indicates that iron dissolves from precipitates in grain boundaries and diffuses into the grains during the process. It was found that iron represents a major part of the active defect concentration in the investigated multicrystalline material after the applied oxidation process
Determination of spatially resolved trapping parameters in silicon with injection dependent carrier density imaging
We present spatially resolved and injection dependent excess carrier lifetime measurements on silicon. At low level injection conditions an anomalous increase often interferes in such measurements. The origin of the anomalous increase is discussed. Assuming trapping as the origin, highly resolved images of trap parameters together with low level injection recombination lifetimes with strongly reduced trapping effects have been obtained. A theoretical model for infrared lifetime imaging based on the Hornbeck and Haynes model [J. A. Hornbeck and J. R. Haynes, Phys. Rev. 97, 311 (1955)] is presented which describes the trapping effect on the measured lifetime. This model is fitted to experimental spatially resolved data to extract trapping parameters, particularly trap density and the trap-escape ratio, i.e., the ratio between escape rate of minority carriers from the trap level into the minority band (detrapping) and trap rate from the minority band into the trap level (trapping). An upper bound for the low...
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