Chemical equilibrium description of stable and metastable defect structures ina-Si:H

Influence of the statistical shift of Fermi level on the conductivity behavior in microcrystalline silicon

“…9 Another situation is where the anti MNR is more pronounced at values of E a on the lower side, when the DOS value at the minimum reduces. 9 Such a reduction in DOS value at the minimum, where exponential CB and negatively charged dangling bond (DB -) tails meet, has been observed in the case of n-type doping of a-Si:H. 37,38,39 Here DOS of DB -band increases with increased doping level. The failure of MNR at higher E a side can be seen when E f lies far in the tail of the DB -states or in intrinsic materials where DOS at the mid gap is almost flat, due to which the temperature derivative of E f will be very little or almost zero.…”

Correlation between the results of charge deep-level transient spectroscopy and ESR techniques for undoped hydrogenated amorphous silicon

“…Note that the spectrum for the annealed state is identical for both models but for different values of fitting parameters ͑see Table II͒. and D e defects over the neutral D z ones, predicted by improved defect-pool model, 7,9 . For the annealed state lower total density of states is obtained by Powell and Dean 7 in comparison with Schumm 9 ͑by factor of 1.6͒. For the LS state Schumm's model overestimates the density of charged ͑mainly D h ) gap states.…”

“…4 and 5, and obtained values of fitted parameters lead to several conclusions. Powell and Dean's and Schumm's models 7,9 can give identical gap state distribution though small differences in the fitted parameters are required ͑see 9 Two values of the quasi-Fermi levels were obtained as the best fit to experimental spectra 6 and 7 in Fig. 1 Fig.…”

“…As a result of the first DLTS measurements on undoped a-Si:H based MOS structure, we have observed three groups of states, with mean energies of 0.63, 0.82, and 1.25 eV, in a good agreement with the existence of the D h ,D z , and D e dangling bond states, respectively, predicted by improved defect-pool model. [7][8][9][10] All of these referred papers are based on the defect-pool concept which was excellently described in a classic paper by Winer. 11 According to the defect-pool model, the defect chemical potential depends on the Fermi energy and a shift of the Fermi level at the equilibration temperature should change the proportions among the densities of D h ,D z , and D e components.…”

“…We compare the experimental charge DLTS spectra with those obtained as a result of simulations based on the improved defect-pool model. 7,9 Also, the electronic density of states, Ϫ2 for 5 min. After ArBB, the vacuum system was filled with molecular oxygen.…”