Optical enhancement of the electron paramagnetic resonance signal from SiIII centers at the Si/SiO2 interface

The EPR signal Pb from interface SiIII centers in oxidized (111) and (100) silicon wafers has been observed to be enhanced up to 20 times under illumination with white light at liquid-nitrogen temperature. The enhanced EPR signal saturates normally with microwave power, much like its unenhanced counterpart, which indicates that it is not a photoconductive pseudo-EPR signal, as observed for other silicon surface defects. It is suggested that the effective spin polarization of SiIII centers is changed by the light. The optical effect, however, shows complications which may reflect coupling between the Pb center and the semiconductor carriers.