IDENTIFICATION OF THE DOMINANT ELECTRON DEEP TRAP IN AMORPHOUS-SILICON FROM ESR AND MODULATED PHOTOCURRENT MEASUREMENTS - IMPLICATIONS FOR DEFECT MODELS

Modulated photocurrent (MPC) measurements in intrinsic a-Si:H reveal a prominent band of electron traps with a thermal emission energy near 0.6 eV. We have identified this defect band by comparing MPC and elect ron paramagnetic resonance spectra for intrinsic and lightly n-type do ped samples over a range of metastable states. These data directly sho w that the MPC band arises from the neutral charge state of the defect s. This identification is also confirmed when the quasi-Fermi level is varied by the application of light bias. Such observations are totall y inconsistent with a large population of charged defects in intrinsic samples predicted by recent versions of the defect pool model. Rather , our observations have a natural explanation in terms of a defect rel axation process. (C) 1998 Elsevier Science B.V. All rights reserved.