Bulk photovoltaic effect in GaNGeC quaternary compound semiconductors

Compared to the p-n junction photovoltaic effect, the bulk photovoltaic effect is a potential way to overcome the external limitations of solar energy conversion. It is challenging to find new materials with a bulk photovoltaic effect. In this article, using first-principles calculations and the maximum local Wannier function, we investigated the bulk photovoltaic effect in GaNGeC quaternary compound semiconductors with six different crystal structures (S-1, S-2, S-3, S-4, S-5, and S-6 for short). These semiconductors showed a large effective three-dimensional shift current conductivity, where the maximum absolute value of the shift current conductivity ranges from 10 μA V^-2 to 425 μA V^-2, indicating that they are promising candidates for photoelectric conversion applications. Furthermore, the electron localization function, difference charge density, and atomic configurations as well as Löwdin population analysis revealed that dimerization of the GaN layer and the GeC layer in S-5 and S-6 induces delocalization of electrons. This delocalization of electrons enhances their shift current conductivities, which provides valuable insight for further design and development of new photovoltaic materials.