Determination of carrier lifetime in Si by optical modulation

Abstract

A contactless optical modulation technique for the determination of photogenerated carrier lifetime in silicon is presented. The method is based on the measurement of the optically modulated free-carrier absorption in Si at 10.6 µm. The fractional change in transmitted intensity of a dc below band-gap probe beam (with ħω_{p} E_{g}) is proportional to the excess carrier lifetime. This optical modulation technique, which is relatively simple, contactless, and nondestructive, may have significant potential as a high-resolution high-sensitivity tool for Si wafer screening, crystal growth studies, and process evaluation.