Generalized analysis of quasi-steady-state and quasi-transient measurements of carrier lifetimes in semiconductors

Recently, a simple yet powerful carrier lifetime technique for semiconducto r wafers has been introduced that is based on the simultaneous measurement of the light-induced photoconductance of the sample and the corresponding l ight intensity [Appl. Phys. Lett. 69, 2510 (1996)]. In combination with a l ight pulse from a flash lamp, this method allows the injection level depend ent determination of the effective carrier lifetime in the quasi-steady-sta te mode as well as the quasi-transient mode. For both cases, approximate so lutions (those for steady-state and transient conditions) of the underlying semiconductor equations have been used. However, depending on the actual l ifetime value and the time dependence of the flash lamp, specific systemati c errors in the effective carrier lifetime arise from the involved approxim ations. In this work, we present a generalized analysis that avoids these a pproximations and hence substantially extends the applicability of the quas i-steady-state and quasi-transient methods beyond their previous limits. (C ) 1999 American Institute of Physics. [S0021-8979(99)07922-0].