  Bismuth telluride is a low energy bulk band-gap topological system with
conducting surface states. Besides its very good thermoelectric properties, it
also makes a very good candidate for broadband photodetectors. Here, we report
temperature-dependent photo-Seebeck effect in a bulk single crystalline bismuth
telluride. On light illumination, an electrically biased sample shows
distinguishable contributions in the measured current due to both the Seebeck
effect and the normal photo-generated carriers within a narrow layer of the
sample. Detailed experiments are performed to elucidate the distinction between
the Seebeck contribution and the photogenerated current. The
temperature-dependence of the photocurrent without Seebeck contribution shows a
sign reversal from negative to positive at a specific temperature depending on
the wavelength of photoexcitation light.
