Experimental evidence for zero-correlation-energy deep defects in intrinsic hydrogenated amorphous silicon

Abstract

Depletion-width-modulated ESR spectroscopy together with junction-capacitance techniques yield the total spin and charge change associated with the emission of electrons from deep defects (D) in intrinsic a-Si:H samples. We find that, in contrast to n-type doped samples, the predominant transition is from the ${\mathit{D}}^0$ to ${\mathit{D}}^{+}$ charge state near midgap. However, the magnitude of spin to charge change is too small for a defect having a significantly positive correlation energy, ${\mathit{U}}_{\mathit{e}\mathit{f}\mathit{f}}$; rather, it agrees with a nearly zero value of ${\mathit{U}}_{\mathit{e}\mathit{f}\mathit{f}}$ (-50<${\mathit{U}}_{\mathit{e}\mathit{f}\mathit{f}}$<+80 meV) between the singly and doubly occupied charge states.