Use of Tetraethylgermane in ArF Excimer Laser Chemical Vapor Deposition of Amorphous Silicon-Germanium Films

A new organogermanium precursor, tetraethylgermane (TEGe, Ge(C2H5)4) was used with disilane in ArF excimer laser chemical vapor deposition of hydrogenated amorphous silicon-germanium films (a-Si1-xGex:H,C). The germanium composition, x, could easily be controlled since it almost coincided with the gas-phase composition. The optical band gap (E opt) of the film was reduced from 1.8 eV (x=0) to 1.4 eV (x=0.8). This relatively wide E opt compared with conventional hydrogenated or fluorinated silicon-germanium, was ascribed to the carbon corporation and dominant SiH2 and GeH2 bonds in the film.