Published online by Cambridge University Press: 25 February 2011
We compare the experimentally observed correlation between the density of charged dangling–bond defects and the Fermi–level position in n– and p–type a–Si:H films with the predictions of two hydrogen–related models for the thermal equilibrium state at the glass–transition temperature of the hydrogen glass in a–Si:H. Reasonable agreement is obtained with a defect reaction in which the transfer of hydrogen from Si–H bonds to weak bonds is limited to distances comparable to one atomic spacing. The results for p–type (boron–doped) films suggest that the formation of positively charged dangling–bond defects is not only determined by electronic energy differences but also by a relaxational energy gain of approximately 0.2eV.