DETERMINATION OF THE PHOTOCARRIER LIFETIME IN AMORPHOUS-SILICON WITH THE MOVING PHOTOCARRIER GRATING TECHNIQUE

In this paper we have determined the lifetime of photogenerated carriers in semiconductors using a technique that does not require time or frequency resolved measurements of the photoconductivity. The lifetime is deduced from the DC-short circuit current that is induced by a laser interference grating of period and moving along the semiconductor surface with the velocity v(gr). We observe a maximum short circuit current density j(sc) at a velocity that corresponds to a frequency omega(max) = 2piv(max)/and of the moving interference grating. Based on a theoretical analysis of j(sc) we show that omega(max) equals the inverse of the photocarrier lifetime tau, if the dielectric relaxation-time tau(diel) is short compared to tau and if the grating period is chosen large compared to the ambipolar diffusion length.