This study reports the spontaneous formation of 2D magnesium (Mg)-intercalated gallium nitride (GaN) superlattices through annealing a metallic Mg film on GaN at atmospheric pressure. This process, characterized as interstitial intercalation, results in a significant uniaxial compressive strain perpendicular to the interstitial layers, with the GaN layers exhibiting an exceptional elastic strain exceeding -10%. The strain alters the electronic band structure and enhances hole transport along the compression direction. Additionally, the Mg sheets induce a periodic transition in GaN polarity, generating polarization-field-induced net charges. These findings offer new insights into semiconductor doping, conductivity enhancement, and elastic strain engineering of nanomaterials and metal-semiconductor superlattices. The study also highlights the perfect lattice match between GaN and Mg, which reduces the lattice mismatch strain and facilitates the spontaneous formation of 2D-Mg on GaN. The enhanced hole transport and modified surface potential of GaN due to the MiGs structure have technological implications, such as improved barrier height for n-type Schottky barrier diodes and reduced contact resistivity for p-type GaN, enabling ohmic contact.This study reports the spontaneous formation of 2D magnesium (Mg)-intercalated gallium nitride (GaN) superlattices through annealing a metallic Mg film on GaN at atmospheric pressure. This process, characterized as interstitial intercalation, results in a significant uniaxial compressive strain perpendicular to the interstitial layers, with the GaN layers exhibiting an exceptional elastic strain exceeding -10%. The strain alters the electronic band structure and enhances hole transport along the compression direction. Additionally, the Mg sheets induce a periodic transition in GaN polarity, generating polarization-field-induced net charges. These findings offer new insights into semiconductor doping, conductivity enhancement, and elastic strain engineering of nanomaterials and metal-semiconductor superlattices. The study also highlights the perfect lattice match between GaN and Mg, which reduces the lattice mismatch strain and facilitates the spontaneous formation of 2D-Mg on GaN. The enhanced hole transport and modified surface potential of GaN due to the MiGs structure have technological implications, such as improved barrier height for n-type Schottky barrier diodes and reduced contact resistivity for p-type GaN, enabling ohmic contact.