Strain-induced enhancement of 2D electron gas density in AlGaN/GaN heterojunction: a first-principles study

In this study, we investigated the impact of strain on the electronic structure and polarization of Al x Ga1-x N and AlGaN/GaN heterojunctions using first-principles density functional theory. Our findings reveal that, in the absence of strain, the band gap and electron effective mass of Al x Ga1-x N increase with higher Al composition. Similarly, the spontaneous and piezoelectric polarization also increase accordingly. Moreover, under biaxial 5% tensile strain and 5% compressive strain, the two-dimensional (2D) electron gas surface density in the AlGaN/GaN heterojunction reaches 8.12 x 1012 cm-2 and 2.50 x 1012 cm-2, respectively. Comparatively, the surface density without strain is 5.62 x 1012 cm-2. Tensile strain significantly enhances the 2D electron gas surface density, which holds potential theoretical value for improving the electrical performance of AlGaN/GaN high electron mobility transistors.