Sonochemical Modification of SiGe Layers for Photovoltaic Applications

To improve the photovoltaic response of SiGe and amorphous silicon (a-Si)/SiGe surfaces, a sonochemical treatment in chloroform (CHCl₃) is used. The use of the sonochemical reaction slows down the observed surface photovoltage (SPV) decay and enhances its magnitude in SiGe and a-Si/SiGe thin layers grown on Si. The average surface-integrated photovoltage and decay time can increase up to 50%. This effect is not observed in distilled water, indicative of the fact that CH-containing radicals can lead to the observed improvements. It is suggested that the effect can be explained as follows: CHCl₃ is decomposed and produces hydrocarbon chains, which are then decomposed further away into hydrogen and carbon. The reactive Si dangling bonds revealed on the surface of SiGe alloys are saturated by the hydrocarbon species to passivate the surface. It is, therefore, advantageous to use sonochemical surface modification of silicon–germanium-based photovoltaic materials in chloroform solutions.