Characterization of multiple Si/SiO ₂ interfaces in silicon-on-insulator materials via second-harmonic generation

Charge generation, transport, and recombination processes in UNIBOND™ silicon-on-insulator wafers are studied via an optical second-harmonic generation (SHG) technique. The electric fields at the interfaces vary with time due to charge trapping. The presence of a thin native oxide layer on the top Si film contributes significantly to the SH intensity due to the strong time-dependent electric field generated by electrons transported to the surface. For the thick buried oxide, the electric field is primarily due to carrier trapping at the interface, and it varies with time weakly. The SHG signals depend strongly on the externally applied electric field, which can differentiate the contribution of each interface to the total SH signal.