Urbach tails of amorphous silicon

Urbach tails of amorphous silicon

In earlier work, we showed that exponential (Urbach) band-edge states were localized on connected subnetworks of short bonds for the valence tail and long bonds for the conduction tail for high-quality continuous random network models of amorphous silicon. Here, we study size effects by computing the electronic density of states for a 105-atom model of α-Si proposed by G. T. Barkema and N. Mous...

Atomistic origin of urbach tails in amorphous silicon.

Exponential band edges have been observed in a variety of materials, both crystalline and amorphous. In this Letter, we infer the structural origins of these tails in amorphous and defective crystalline Si by direct calculation with current ab initio methods. We find that exponential tails appear in relaxed models of diamond silicon with suitable extended defects that emerge from relaxing point...

Electron-drift-mobility measurements and exponential conduction-band tails in hydrogenated amorphous silicon-germanium alloys.

We have measured the temperature dependence of the electron drift mobility using the time-offlight technique for a series of undoped hydrogenated amorphous silicon-germanium alloys with band gaps spanning the range 1.47-1.72 eV. We also developed techniques for analyzing dispersion effects in such measurements, which permitted us to compare essentially all previous measurements with our own. We...

Defects in Amorphous Semiconductors: Amorphous Silicon

Defects in disordered (amorphous) semiconductors are discussed, with an emphasis on hydrogenated amorphous silicon. The general differences between defect phenomena in crystalline and amorphous hosts are described, and the special importance of the electron–phonon coupling is stressed. Detailed calculations for amorphous Si are presented using accurate first principles (density-functional) tech...

Multilayered Amorphous Silicon Structures