Polarity inversion and electronic structure in magnesium-induced GaN inversion domain superlattices

Abstract

In this study, we propose and investigate three atomic configurations of magnesium (Mg)-induced GaN inversion domain superlattices (denoted as IDBNa, IDBNb and IDBNc) using first-principles density functional theory. Detailed electronic structure analysis reveals that periodic polarity inversion at inversion domain boundaries induces the formation of two-dimensional carrier gases and periodic band bending. These features also lead to local band-gap narrowing and modify the spatial distribution of electronic structure along the c-axis. Defect calculations show that Ga vacancies and substitutional Mg atoms typically form near Mg intercalations, whereas N vacancies tend to localize farther away under different ambient growth conditions. These defects exhibit strong spatial localization, significantly affecting the local electronic structure. Furthermore, Mg segregation at inversion boundaries is found to be energetically favorable at fractions below or around 3/2 monolayers, maintaining near-monolayer structural characteristics. As Mg segregation increases, the built-in polarization fields are gradually compensated, which reduces band bending and modifies the spatial distribution of electronic structure compared with the non-segregated IDBNc superlattices. The combined effects of structural polarity inversion, localized defect formation, and Mg segregation provide critical insights into band structure modulation in Mg-induced GaN inversion domain superlattices. These findings provide a theoretical foundation for understanding the electronic structure, defect characteristics and the formation mechanism of Mg-induced GaN inversion domain superlattices, offering pathways for interface and defect engineering to optimize p-type conductivity in high-performance GaN-based electronic and optoelectronic devices.