Transport and Recombination Channels in Undoped Microcrystalline Silicon Studied by ESR and EDMR

Abstract

ABSTRACTWe present a detailed study of ESR and spin-dependent transport (EDMR) on μc-Si. We identify to different types of defects at g=2.0055(±3) and g=2.0044(±5) and study their influence on transport and recombination by stepwise annealing the samples. We find that transport is not controlled by defects if ND<1018 cm−3. For ND>1018cm−3 a dramatic decrease of the conductivity is found and we identify a hopping contribution in transport. To explain our ESR and EDMR results we propose a simple model where most defects are distributed at the surface of the columns and transport is along percolation paths. We also observe minor metastable changes of the defect density which are assigned to adsorption of atmospheric oxygen.