Stress and doping impact on intrinsic point defects in silicon and germanium

Abstract

Although the impact of stress on the formation and migration energies of the intrinsic point defects in Si is small, it is shown that its impact on the intrinsic point defect distribution during crystal growth from a melt is unexpectedly large. Due to this significant impact on single crystal and wafer quality, stress effects should therefor be taken into account for the development of the next generation large diameter crystals. Besides stress, also impurities change the intrinsic point defect distribution by various mechanisms such as trapping, introduction of additional internal stress and shifting of the Fermi level leading to intrinsic point defects in different charge states and with different formation energies. The relative importance of these contributions is discussed and compared. Last not but least also interfaces or free surfaces have an important impact both on the formation energy and the introduction of intrinsic point defects from that surface into the bulk.