Built-in electric fields and valence band offsets in InN/GaN(0001) superlattices: First-principles investigations

Based on all-electron density functional theory calculations, we systematically investigate the built-in electric fields and valence band offsets in wurtzite InN/GaN(0001) superlattices, where their correlations with biaxial strain, as well as the superlattice geometry, are determined. Both the built-in electric fields (several MV/cm) and the valence band offsets (0.16 –1.1 eV) are found to be strongly dependent on the superlattice geometry and strain growth conditions. Spontaneous polarization and strain-induced piezoelectric polarization are comparable in contribution to the macroscopic electric field. Relative to the fully relaxed superlattices, tensile (compressive) strain significantly weakens (strengthens) the magnitude of the electric field, and decreases (increases) the value of the valence band offset. The results will be valuable in relation to practical heterojunction-based device optimization and design.