Wavelength dependence of the surface photogalvanic effect in CuSe film

We demonstrate the changing sign of the surface photogalvanic effect current in a film consisting of CuSe nanocrystallites in an amorphous Se matrix in a wide spectral range. The longitudinal and transverse photocurrents were measured as functions of polarization state of the excitation beam and its incidence angle in the spectral range of 355–1064 nm. It was found that the longitudinal photocurrent flows in opposite directions at 532 and 725 nm (825 and 1064 nm) for the p-polarized (s-polarized) excitation beam. The longitudinal photocurrent excited by p-polarized light is much higher than that excited by s-polarized light. Both for the elliptically and linearly polarized excitation, the transverse photocurrent changes the sign between 532 and 725 nm. Such a reversal of photocurrent flow is explained by the photoexcitation of light and heavy holes bands, which have different momentum distribution of excited carriers. The data obtained provide deeper understanding of surface photogalvanic effect in nanocomposites and are of interest for optoelectronics.