Correlation between electronic polarization and shift current in cubic and hexagonal semiconductors LiZnX (X=P,As,

The rectified bulk photovoltaic effect (BPVE) in noncentrosymmetric semiconductors, also called shift current, is considered promising for optoelectronic devices, terahertz emission, and possibly solar energy harvesting. A clear understanding of the shift current mechanism and search for materials with large shift current is, therefore, of immense interest. $ABC$ semiconductors $\mathrm{LiZn}X$ $(X=\mathrm{N}, \mathrm{P}, \mathrm{As}, \text{and} \mathrm{Sb})$ can be stabilized in cubic as well as hexagonal morphologies lacking inversion symmetry---an ideal platform to investigate the significant contributing factors to shift current, such as the role of structure and chemical species. Using density-functional calculations properly accounting for the electronic bandgaps, the shift current conductivities in $\mathrm{LiZn}X$ $(X=\mathrm{P}, \mathrm{As}, \mathrm{Sb})$ are found to be approximately an order of magnitude larger than the well-known counterparts and peak close to the maximum solar radiation intensity. Notably, hexagonal LiZnSb shows a peak shift current conductivity of about $\ensuremath{-}75\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{A}/{\mathrm{V}}^{2}$ and Glass coefficient of about $\ensuremath{-}20\ifmmode\times\else\texttimes\fi{}\phantom{\rule{4pt}{0ex}}{10}^{\ensuremath{-}8} \mathrm{cm}/\mathrm{V}$, comparable to the highest predicted values in literature. Our comparative analysis reveals a quantitative relationship between the shift current response and the electronic polarization. These findings not only posit Li-Zn-based $ABC$ semiconductors as viable material candidates for potential applications but also elucidates key aspects of the structure-BPVE relationship.