Surface photovoltage phase spectroscopy – a handy tool for characterisation of bulk semiconductors and nanostructures

A new approach is proposed for determining the semiconductor conductivity type (n or p) based on measurements of surface photovoltage (SPV) phase spectra in metal–insulator–semiconductor structures under modulated super-bandgap optical excitation. It is shown that the sign of the bandgap-related knee in the spectrum of the SPV phase modulus gives information about the surface band bending direction and thus about the semiconductor type. The proposed approach can be applied also to multilayered structures, containing buried interfaces in order to obtain the band bending in the sample region, where the light is absorbed. Further on, the SPV phase spectral dependence is discussed taking into account the recombination processes in the system under study. It is concluded that for the cases of non-linear recombination the SPV phase spectrum reveals the peculiarities of the optical absorption coefficient spectrum, which is known until now only for the SPV amplitude spectrum. This is confirmed by SPV phase and amplitude spectral measurements in bulk Si, as well as in GaAs quantum wells.