Phase-sensitive LBIC analysis

We built a setup for local current and voltage analysis as well as reflection measurements. The sample is illuminated by four amplitude-modulated diode lasers with wavelengths of 635 nm, 835 nm, 910 nm and 980 nm coupled into one optical fibre. The phase shift introduced by the solar cell depends on carrier lifetime, carrier diffusion velocity, time delay in both instrument and sample and the impedances incorporated in the solar cell itself. At a reference frequency of 1 kHz, the phase shift introduced by carrier lifetime and diffusion dynamics is around 1/spl deg/, the solar cell's internal capacitors and resistors introduce a phase shift of up to 70/spl deg/. Significant structure in phase maps is only visible in the long wavelength range (833 nm, 910 nm and 980 nm).