Highly photoconductive 1.4-1.5 eV amorphous silicon germanium alloys prepared by dc-glow discharge

Amorphous hydrogenated SiGe alloys have been prepared in a dc-glow discharge in a diode as well as in a triode reactor from SiH4/GeH4 mixtures with and without H2 dilution at different gas compositions. The SiGe films prepared from H2-diluted gases and/or in a triode configuration exhibit excellent AM1 photoconductivity of 2 x 10 -4th 1/ohm cm (Eg = 1.5 eV) and 10 to the -5th 1/ohm cm (Eg = 1.4 eV). Analysis of the temperature-dependent conductivity indicate EF near midgap and films to be fairly intrinsic. No indication for crystalline phases has been observed from Raman backscattering experiments. Valence and conduction band tailing evaluated from PDS or time-of-flight and TPC transient-photo current measurements reveal characteristic energies of about 50 meV and 30 meV, respectively.