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

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 D⁰ to 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, Ueff; rather, it agrees with a nearly zero value of Ueff (-50Ueff+80 meV) between the singly and doubly occupied charge states.