Heteroepitaxial growth and interface band alignment in a large-mismatch CsPbI3/GaN heterojunction

Abstract

The development of high-quality GaN-based heterojunctions breaks through the limitation of lattice mismatch, which is of particular importance for promoting their optoelectronic applications. Herein, we report the incommensurate heteroepitaxial growth of single-crystal cesium lead iodine (CsPbI₃) nanoplatelets on a c-GaN/sapphire substrate with a uniform rectangular shape and composition distribution via one-step chemical vapor deposition. The formed CsPbI₃/GaN heterojunction presents a type-II band alignment with the valence and conduction band offsets of 2.12 ± 0.15 eV and 0.60 ± 0.15 eV, respectively. Compared with CsPbI₃ grown on a mica substrate, the CsPbI₃/GaN heterojunction exhibits remarkable photoluminescence quenching and a shorter exciton lifetime, which arises from the enhanced carrier separation and extraction efficiencies induced by the band-offset effect. Thanks to the complementarity between the band gaps of CsPbI₃ and GaN, the optical absorption of the formed heterojunction is expanded from the visible light to ultraviolet. These findings suggest the large potential of the CsPbI₃/GaN heterojunction for the development of high-performance integrated photovoltaic and optoelectronic devices.