Doped a-Si H above the equilibration temperature

Conductivity data for n-type and p-type samples above the equilibration temperature are shown in Fig. 7.4 and similar data are in Fig. 5.2. The conductivity is activated with a prefactor of 100-200 cm for both doping types and the activation energy is 0.3-0.4 eV in n-type material and 0.4-0.6 eV in p-type. In the thermal equilibrium regime, the Fermi energy is pinned by the defect and dopant states and consequently the statistical shift is small, as is discussed in Section 6.2.2. Yp may be calculated from a numerical 

The first term on the right hand side of Eq. (7.18) is the usual statistical shift determined at a constant electron density. However, the electron density is itself temperature dependent above the equilibration temperature because of the structural changes. The second term on the 

The Fermi energy in doped samples is within the band tail, so there should be no significant contribution to the conductivity from the temperature dependence of the band gap. Thus, in the absence of any temperature dependence of E, is equal to the measured conductivity prefactor. 

A conductivity prefactor of 100-200 ft cm gives the free carrier mobility from Eq. (7.5), 

Note that the relation between ji, and includes a factor of T. The analysis of the conductivity data is slightly different if p, or is assumed to be independent of temperature. However, since the experiments cover a small temperature range and it is not known if there is any other temperature dependence to ct, there is no guide as to which is the more appropriate assumption. 

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