STRUCTURAL AND OPTOELECTRONIC PROPERTIES OF GE-RICH HYDROGENATED AMORPHOUS SILICON-GERMANIUM ALLOYS

In this work the structural and opto-electronic properties of rf sputtered germanium-rich hydrogenated amorphous silicon germanium alloys (a-SixGe1-x:H) are presented. It has been found that for x less-than-or-equal-to 0.1, the Si incorporation does not appreciably affect, either the density of localized states in the pseudo-gap, or the structural properties of the films. However the Tauc's optical gap shifts from 1.04 eV (x=0.0) to almost-equal-to 1.13 eV (x=0.1). A concomitant two orders of magnitude decrease of the dark conductivity is measured, whereas the photoconductivity remains essentially unchanged. In other words, the incorporation of small amounts of Si in the hydrogenated amorphous germanium (a-Ge:H) network produces a noticeable increase of the photosensitivity of the samples. These results are discussed in the framework of present models of amorphous semiconductor alloys.7642473247