First-principles study on electrical and optical properties of two-dimensional GaN/AlGaN heterostructures

Based on first-principles, this paper calculates the structure, electrical properties and optical properties of g-GaN/AlGaN 2D/3D heterojunctions with different Al contents. By comparing the binding energies of different Al contents, it can be concluded that the structure of heterojunction is the most stable when the Al content is 0.5. The band gap of heterojunction widens as the Al content increases. When the Al content is 1, the band structure changes from direct band gap to indirect. Through the study of density of states, it can be found that impurity levels near the Fermi level mainly come from electronic states of N 2p, Al 3p, and Ga 4p. The appearance of impurity levels makes it easier to recombine the electron hole pairs in the heterojunction. The results of optical properties indicate that the heterojunction exhibits better wave absorption performance with the increase of Al content and is more conducive to the propagation of photoelectrons.