Investigation of SiO/sub 2/ film on Si substrate by photoacoustic method

The effect of SiO/sub 2/ film on Si substrata (SiO/sub 2//Si) was investigated by photoacoustic spectroscopy. The amplitude and phase spectra were measured and analyzed in dependence on the wavelength of excitation optical beam. The amplitude PA spectra of Si wafer are analogous to the optical absorption spectra. On the other side, the amplitude PA spectra of SiO/sub 2//Si sample show the significant difference. In the energy range above the energy gap of Si, the spectral characteristic has a typical form for optical interference. The phase PA spectra of Si wafer and SiO/sub 2//Si structure are the same in the energy range above the energy gap of Si. In the energy range below the energy gap of Si, the PA spectra of Si wafer and SiO/sub 2//Si structure show the significant difference. The PA signal in this case is the consequence of the electronic states formed on dielectric-semiconductor interface, i.e., the influence of the interface trapped states on the thermal and electronic transport processes in SiO/sub 2//Si junction.