Large bulk photovoltaic effect and Fermi-surface-mediated enhancement with chemical potential in ZnGeP2.

Abstract

Bulk photovoltaic effect is a non-linear response in noncentrosymmetric materials that converts light into DC current. In this work, we investigate the optical linear and non-linear responses in a chalcopyrite semiconductor ZnGeP₂. The reference point for chemical potential (E_f) appears at the valence band maximum of high symmetry Γ point in Brillouin zone for ZnGeP₂. We report large bulk photovoltaic namely shift and circular photogalvanic current conductivities which are 4.46µA V^-2and -5.49µA V^-2respectively with the incident photo energy around ∼5 eV at the chemical potential ofE_f= 0 eV which increase about 38% and 81% respectively at a chemical potential ofE_f= 1.52 eV. The systematic evolution of the bulk Fermi surface along with the high symmetry points in three dimensional Brillouin zone reveals the enhancement of bulk photovoltaic with the chemical potential in ZnGeP₂. We further explore the distribution of bulk projected band and surface Fermi surface distribution in the energy landscape using tight binding Hamiltonian within semi infinite slab geometry. The augmentation of bulk photovoltaic with the chemical potential is due to the projected bulk bands along the high symmetryΓ-Zdirection in Brillouin zone. Our thorough and detailed study not only provide a deeper understanding about the role of Fermi surface contribution to the bulk photovoltaic responses with chemical potential, but also suggest ZnGeP₂as an ideal candidate for optoelectronics and bulk photovoltaic.