Band Tailing and Transport in a-SiGe:H-Alloys

Optical and transport studies of both cb- and vb-tail states in a-Si 1−x Ge x :H such as subband absorption (PDS), instationary photocurrent experiments (TOF, PTS) for electrons and holes, Modulated Photocurrent Spectroscopy (MPS), and Raman scattering have been performed. The main consequences of Ge-alloying into the a-Si:H network are i) an increase in cb-tail state density at the conduction band edge and in the exponential cb- tail even for small x (O vo ≈(50–60) meV). Halfwidths of Raman TO-like modes point to the existence of a rigid Si-network in O 0.35 into a Si-Ge compound structure with maximum disorder at x≈0.5.