Correlation between electronic polarization and shift current in cubic and hexagonal semiconductors LiZn$X$ ($X$ = P, As, Sb)

TL;DR

This study investigates the shift current in LiZnX semiconductors, revealing that their electronic structure and polarization significantly influence their photovoltaic response, with potential for optoelectronic applications.

Contribution

It provides the first detailed analysis of the relationship between electronic polarization and shift current in cubic and hexagonal LiZnX semiconductors, highlighting their high shift current conductivities.

Findings

LiZnX semiconductors exhibit large shift current conductivities.

Hexagonal LiZnSb shows peak shift current comparable to top literature values.

A quantitative link between electronic polarization and shift current is established.

Abstract

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 LiZn$X$ ($X$ = N, P, As, and 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 LiZn$X$ ($X$ = P, As, 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 $\sim -75 ~\rm{\rm{\mu}}$A/V$^2$ and Glass coefficient of $ -20$ $\times$ 10$^{-8}$ cm/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.