Shell Composition-Mediated Band Alignment and Defect Engineering in Indium Phosphide-Based Core/Shell Quantum Dots

Abstract

Realization of a suitable energy band structure of core–shell-structured indium phosphide (InP)-based quantum dots (QDs) is crucial for their anticipated use in various optoelectronic devices. In this study, we demonstrate how to achieve the optimal band alignment and defect engineering of InP core/Zn_1–xCd_xSe shell QDs by systematically varying the shell composition. Using advanced spectroscopic techniques, we show how the alloyed Zn_1–xCd_xSe shell reduces surface defects while simultaneously tuning the charge carrier wave functions from localization to delocalization mode due to the band alignment shift from type-I to quasi-type-II. These InP-based core/shell QDs also exhibit outstanding stability under high-energy ultraviolet irradiation and thermal treatment, as well as long-term storage stability, which is essential for device applications. Furthermore, studies using floating gate transistors based on InP-based core/shell QDs demonstrate the synergistic influence of the energy band structure and defects on charge injection and the spontaneous recovery of the trapped charges.