Transient and quasi-steady-state photoconductance decay measurements of lifetime are the limiting cases of the general equation given as 1.

In the case of transient measurements, the pulse of light is only to excite the carriers and is off during the actual measurement so that G(t) = 0. For the QSS measurements, it is assumed that the light is varying very slowly so that d(Δn)/dt = 0.

The generalized form of the equation is useful when the flash and wafer have similar time constants.

- 1. , «Generalized analysis of quasi-steady-state and quasi-transient measurements of carrier lifetimes in semiconductors», Journal of Applied Physics, т. 86, с. 6218-6221, 1999.