Vegard's-law-like dependence of the activation energy of blistering on the x composition in hydrogenated a-SixGe1-x

Surface quality is a key issue in semiconductor structures for device applications. Typical surface defects are blisters. Here we investigate on the relationship between the activation energy of blistering and the composition x in hydrogenated amorphous a-SixGe1-x by employing layers deposited by Radio Frequency sputtering. To this aim the blistering activation energy was determined by means of Arrhenius plots in several samples with different compositions, including x = 0 and x = 1. Each sample was submitted to heat treatment up to the temperature where the onset of blistering was observed by change of the surface reflectivity. It is found that a linear dependence of the activation energy on x similar to the Vegard's law holds. The experimental result is supported by reaction kinetics modeling. It is suggested that the key step for the formation of blisters is the scission of the SiH and GeH bonds. The related energetic reaction leading to the formation of H2 molecules in a-SixGe1-x follows a linear law as a function of the x composition similarly to the activation energy.