Defects and Doping in Unconventional Semiconductors

In order for semiconductors to be useful in electronics or optoelectronics, it is crucial to control impurity incorporation and intrinsic point defect formation, often down to parts per million and sometimes even at parts per billion. As technology advances from group-IV (Si), III-V (GaAs, InP, InGaAs), and II-VI (CdTe) semiconductor compounds and their chalcopyrite derivatives (CIGS) to semiconductors with more complicated crystal structures, in 2D or 3D, chemical compositions, or much wider band gaps, the questions of what point defects are prevalent and how to dope these materials p and n-type always arise, challenging both experimentalists and theoreticians. Here, from a theoretical perspective based on density functional theory within standard and beyond approximations, we discuss the fundamentals of doping and defect physics in 2D materials based on transition-metal dichalcogenides, wide-band-gap 3D oxide semiconductors (Ga₂O₃ and CaSnO₃), and organic-inorganic halide perovskites, i.e., materials of current interest to the development of devices. We focus on dopability (both p- and n-type), carrier localization, doping bottlenecks, and possible compensation mechanisms. We hope these insights not only contribute to the fundamental understanding of the physics of defects, but also pave the way for the development of next-generation electronic and optoelectronic devices with enhanced performance and functionality.<br/><br/>This work was funded by the National Science Foundation (NSF) Award #OIA-2217786, and the NSF University of Delaware Materials Research Science and Engineering Center (MRSEC) grant DMR-2011824.