Second-harmonic interferometric spectroscopy of buried interfaces of column IV semiconductors

The technique of combined optical second-harmonic (SH) intensity and phase spectroscopy, which is the spectroscopic modification of SH phase measurements, is proposed to study the nonlinear optical response of semiconductor interfaces with spectrally close resonant contributions. The spectral dependences of SH intensity and phase from oxidised Si (111) and Ge (111) surfaces are studied in the range of 3.5- to 5-eV SH photon energy. The resonant behaviour of combined SH spectra is associated with a superposition of contributions from direct interband transitions at several critical points of Si and Ge band structures.