Dielectric function and electric properties of germanium thin films prepared by gold mediated crystallization

Crystallization of hydrogenated amorphous germanium (a-Ge:H) thin films deposited by plasma enhanced chemical vapor deposition using the GeH4 and H-2 precursors has been investigated. A comparative analysis of the kinetics of the thermal crystallization by annealing to 650 degrees C and of the gold-mediated crystallization (Au-MMC) is carried out. The impact of the Au-MMC on the microcrystalline Ge film microstructure and electrical properties is discussed. The Au thin layer results in a more dense and ordered structure with lower roughness of the microcrystalline Ge films. In order to describe the Ge crystallization kinetics, the dielectric functions of a-Ge:H and microcrystalline germanium mu c-Ge have also been determined by spectroscopic ellipsometry in the range of 0.75-6.0 eV and parametrized using the Tauc-Lorentz dispersion equation.