First principles molecular dynamics study of amorphous   Si\sub{1-x}Ge\sub{x}:H alloys
  We study the structural, dynamical and electronic properties of amorphous Si\sub{1-x}Ge\sub{x}:H alloys using first principles local basis molecular dynamics simulation. The network topology and defects in the amorphous network have been analyzed. Structural changes and an increase in number of defects have been found as the Ge atomic percentage increases from x=0.1 to x=0.5. The electronic density of states exhibits a decreasing band-gap and increased mid-gap and band-tail defect states as Ge concentration increases. Investigation of the band tails of the density of states show an exponential (Urbach) behavior. The mobility gap is estimated as a function of Ge concentration. 
T. A. Abtew and D. A. Drabold