DOPING DEPENDENCE OF 2ND-HARMONIC GENERATION FROM NATIVE OXIDE SI(111) INTERFACES/

Optical second harmonic generation (SHG) was studied on native oxide/S i(111) substrates with both n- and p-type dopings of various doping co ncentrations. With the rotation about the {111} azimuth, six peaks wer e observed in SHG intensity at every 60 degrees with C-3v symmetry for all substrates. However, the strong peaks appeared at 0, 120, and 240 degrees on p-type Si substrates, whereas these peaks were small on n- type Si substrates. We found that the reduction of the peaks at 0, 120 and 240 degrees had a correlation with the change of the doping type and the doping concentration from the p(+) to the n(+) region. Analysi s of the azimuthal rotation dependence of the SH intensity indicates t hat the observed change is caused by the change of the 2nd order non-l inear susceptibility tensor components, chi(z,x,x). We think that this is due to the change of the interface dangling bond occupation and th e resulting change of the interface dipole with the dopings.