Microwave Skin Effect in Noncontact Photoconductivity Decay Measurements in Si Wafers

Abstract

AbstractA formula to calculate the photoconductivity decay curve influenced by the microwave distribution within a silicon wafer has been derived analytically. The difference of photoconductivity decay curves measured at 500 MHz and 10 GHz has been explained by the skin effect and by the comparing the experimental curves to those estimated by the analytical formula. The wafer resistivity and wafer thickness dependent photoconductivity decay curves calculated based on the skin effect have been demonstrated. The results have led to the conclusion that 10 GHz microwave probe scarcely influences on the photoconductivity decay for the silicon wafer with the resistivity >10 Ωcm and a wafer thickness <0.7 mm. For the wafer with a resistivity<10 Ωcm and a wafer thickness>0.7 mm, the photoconductivity decay curve is influenced by the skin effect at 10 GHz. However, the apparent lifetime (or effective lifetime) obtained from the gradient of the tail decay is out of the influence by the microwave skin effect.