Electron transport in the bulk photovoltaic effect

Abstract

The spontaneous motion of electrons in the bulk photovoltaic effect in pyroelectric materials may be explained by separating the processes into two steps: the generation of photoelectrons whose distribution is asymmetric in momentum and a subsequent normal diffusion of the carriers. Asymmetric generation violates time-reversal symmetry and is shown to be only possible for local states in polar systems. Transport properties are calculated for the short-circuit and the open-end case. It is shown that in high-resistivity materials the short-circuit current is not affected by impurities other than those supplying the asymmetric photoelectrons. The open-end saturation field is proportional to the short-circuit current $E_s=\frac{J_{\mathrm{sc}}}{\sigma }$, where $\sigma$ is the photoconductivity. Both results agree with experiment.