Light-soaking and annealing kinetics of majority and minority carrier mobility-lifetime products in a-Si:H

A study on undoped a-Si:H of the light-soaking/annealing process of majority as well as minority carrier properties and their relations to defect density is presented. Defect density was measured by the constant photocurrent method (CPM), electron mobility-lifetime product was deduced from photoconductivity and hole mobility-lifetime product was obtained from measurements of ambipolar diffusion length by steady-state photocarrier grating technique (SSPG). We confirm the already known hysteresis behaviour in the dependence of electron mobility-life time product oil defect density, and report a new and opposite hysteresis-like dependence of the hole mobility-lifetime product during the light-soaking/annealing process. The changes in the mobility-life time products of both carriers and concomitant changes in the defect density and in the Fermi level are discussed on the basis of recombination kinetics and structural order effects. (C) 2002 Elsevier Science B.V. All rights reserved.