Modulated electron-spin-resonance measurements and defect correlation energies in amorphous silicon

We show that thermal modulation of the spin density is determined primarily by the defect correlation energy in intrinsic amorphous semiconductors, and is fairly insensitive to Fermi level position. We present temperature-dependent electron-spin-resonance (ESR) measurements for intrinsic hydrogenated amorphous silicon indicating a correlation energy of about 0.3 eV in low-defect-density material. We discuss the previous interpretation of depletion-width-modulated ESR in intrinsic a-Si:H as indicating a correlation energy of 0.0 eV.