Optoelectronic Properties of Amorphous SiGec Alloys

ABSTRACTWe describe the optoelectronic characteristics of hydrogenated amorphous silicon germanium carbon (a.Si1-x-yGexCy:H) alloys prepared by plasma deposition from SiH4/GeH4/CH4/H2 gas mixtures. a-Si1-x-yGexCy:H is a homogeneous random alloy having a variable optical gap depending on composition, with properties similar to those of amorphous Si-Ge alloys of the same optical gap but with improved thermal stability. Calculations show that if the ratio of Ge/C atomic fractions is 8.2, the average bond length matches that of unalloyed amorphous a-Si:H with the possibility of reduced defect densities at heterointerfaces. After light-soaking with high intensity white light, a sample having a 1.3 eV optical gap exhibited no Staebler-Wronski change in its properties.