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

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

“…The model incorporates both the correlation energy of the defects and also the Fermi level, which may be affected by dopants or by other defects not included in the model. As expected from previous work [5,9], depletion-modulated ESR is quite sensitive to the correlation energy, but it proves to be quite sensitive to the Fermi level as well. Thermal modulation is primarily sensitive to the correlation energy, and is remarkably independent of the Fermi level.…”

“…We chose a value for AE which yields a FWHM width of 0.3 eV; this value is consistent with the optical measurements [6,7], and was used in the previous work on depletion modulation [9]. In Fig.…”

“…Essick and Cohen [9] reported a depletion effect AN s /An~~0A4 for the five different "light-soaking" states of the specimen. They proposed that U-0.0 eV using a similar correlation energy model and density of states to that used here.…”

“…in intrinsic #-Si:H were reported only fairly recently [9]. They were interpreted as evidence for a zero correlation energy, thereby suggesting that most defects in intrinsic <z-Si:H are charged and undetected by ESR.…”

“…1 for a conventional model [6,7,9] In an ideal depletion-modulation experiment, the chemical potential n would be lowered by depleting the total density of electrons n. The new function f\(E) which might result is illustrated by the dashed curve of the middle panel; there is of course a corresponding change in spin density. Lowering the specimen temperature can also affect the spin density; the lower panel of Fig.…”