dc conductivity and the Meyer-Neldel rule in $a$-Si:H

Disorder in amorphous semiconductors results in unusual properties of dc conductivity. We demonstrate a quantitative description of the temperature dependence of conductivity in $a$-Si:H. The universal activation energy dependence of the conductivity prefactor (the Meyer-Neldel rule) is reproduced. Excellent agreement with experimental results is obtained by describing disorder and defects using the general thermodynamic ensemble theory for the structure of disordered systems.