Chemical Interpretation of Charged Point Defects in Semiconductors: A Case Study of Mg2Si

The number of excess charge carriers generated by a point defect, defined by the "charge state" of a defect, is oftentimes an important quantity used to engineer the electronic properties of semiconductors. Here, we develop a molecular orbital theory-based framework for interpreting the charge state(s) of a point defect, which is based on local chemical interactions between the defect and the atoms surrounding the defect site. We demonstrate how the framework can be applied to native defects in Mg2Si, such as interstitials, vacancies, and antisite defects, by utilizing symmetry principles and Density Functional Theory calculations. We anticipate that such an interpretive framework will guide efforts to engineer electronic and optical properties of semiconductors through manipulation of intrinsic and extrinsic defects.