Measurement of defect densities in Ge films grown on Si

Si is used in electronics because of its high conductive properties and cost efficiency. To make Si more optically favorable Ge and GeSn can be grown on top of Si, lowering its band gap. Researchers at AFRL have found a new method of growing Ge on Si using a plasma gas chamber. The newly grown material had to be tested for growth defects to determine if it was consistent with the other materials grown by methods previously used. To test the material, the samples were separated into three Ge layer thicknesses. Using the etchant “Schimmel,” the results showed a decrease in defects as the Ge layer thickened. Two other etchants, “Dash” and “Secco,” both agreed with the negative correlation of defect density as the Ge layer thickened. The density of defects with this new method of growth agreed with literature results for other methods of growing Ge on Si. Two other samples with similar thicknesses of the Ge layer were tested, one annealed for 10 seconds at 750 C and one not annealed. After etching these samples the results showed a large decrease in defects in the sample that was annealed compared to the one that was not. These results show the quality of growth of the material using the new method is consistent with other methods and this technique produces high quality material.