Alignment of thermal donors in Si by uniaxial stress

Thermal donors generated in Czochralski-Si by heat treatment at around 450 °C can be preferentially aligned by applying a large uniaxial stress during their formation process. This alignment is clearly observed by a polarization of the optical transitions of the thermal donors and a corresponding effect for the paramagnetic NL8 centers. Thus a strong correlation between thermal donors and NL8 is again demonstrated, as well as the extended defectlike nature of such defects. The g3 value of the g tensor and the 2p0 dipole oscillator are found to be oriented preferentially perpendicular to the stress direction, a result which seems to disagree with some of the presently discussed thermal donor models.