Structural, optical and electrical properties of hydrogenated amorphous silicon germanium (a-Si1−xGex) deposited by DC magnetron sputtering at high rate

Hydrogenated amorphous silicon germanium alloys (a-Si1−xGex:H) thin films are prepared using DC magnetron sputtering method. The films are deposited under optimized preparation conditions of hydrogen and argon partial pressures at substrate temperature of 150 °C. The relative germanium concentration x was varied between 0 and 0.6. Their structural, optical and electrical properties are investigated. The structural properties of the films are analyzed from the infrared absorption. The hydrogen bond concentration in the films is then deduced using the absorption peaks of stretching mode. The optical band gap Eg of the films determined from the optical transmission measurements decreases uniformly from 2.1 to 1.35 eV when x varies from 0 to 0.6. The conductivity and the photoconductivity measurements are reported. We have observed the increasing of both dark and photo-conductivity when germanium content x increases. All the investigated films properties show a coherent variation with the germanium content.