A pulsed EDMR study of hydrogenated microcrystalline silicon at low temperatures

Abstract

Experimental results of pulsed electrically detected magnetic resonance (pulsed EDMR) measurements are reviewed with regard to the question for microscopic mechanisms that determine the lifetimes of excess charge carriers in hydrogenated microcrystalline silicon. The results show that two qualitatively different dangling bond (db) recombination processes occur. (i) Distant pair recombination through shallow conduction band tail states (CE centers) and dbs and (ii) a db direct capture (dc) recombination where charge carriers localize directly at dbs. For the db–dc process, it is shown that an intermediate, excited triplet state of the db exists which lies about 50meV below the conduction band edge. The recombination probabilities of this path are quantified by means of pulsed EDMR. The temperature and light intensity dependencies suggest that under the experimental conditions given, the db–dc process is not only electronically more active in comparison to the CE–db process, it is even the determining process for the lifetime of excess charge carriers. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)