Electron confinement in a-Si:H and an effective-mass theorem for amorphous semiconductors

In previous work we have shown that the spectral function, rho(kE), must become strongly peaked at the band edges in amorphous semiconductors such as a-Si:H. This fact can be used to construct an effective-mass theorem and the simplest use of the theorem is made to study the effect of confinement in a-Si:H/a-SiNx:H multilayers. We find that the effect of confinement on the density of states is negligible, in apparent disagreement with optical absorption studies of Abeles and Tiedje. However, reanalyzing the absorption coefficient recognizing that only the a-Si:H layers will absorb at the band edges we obtain excellent agreement with experiment and extract parameters describing the electronic structure at the band edge.