Identification of the Dangling-Bond State within the Mobility Gap of a -Si: H by Depletion-Width-Modulated ESR Spectroscopy

The first observation is reported of an absorption (dark) ESR signal specifically from unoccupied gap states within the space-charge region of n-type a-Si: H diode junctions. The detected resonance with g=2.0053±0.0003 is associated with the singly occupied dangling-bond defect. The applied-bias and temperature dependence identifies this signal with the well defined midgap defect band observed in deep-level transient spectroscopy. The results also imply a positive correlation energy, U0.2 eV, between the singly and doubly occupied centers.