Effect of Cu doping on the electronic structure, magnetic and optical properties of GaN/ZnS heterojunctions: a first-principles study

Abstract

In this paper, the GaN/ZnS heterojunction systems with Cu doping and point defects coexisting are calculated by using the generalized gradient approximation in density functional theory, and the electronic structure, magnetic coupling mechanism and optical properties of each system are analysed. The results show that the magnetic source of the systems is twofold, on the one hand, it is the cationic vacancies that cause the unpaired electrons to undergo spin polarization, thus contributing magnetic moments to the system. On the other hand, Cu doping induces the GaN/ZnS heterojunction to produce bound magnetic polaron, which causes the system to undergo a magnetic phase transition, and the concentration of bound magnetic polarons constrains the total magnetic moment of the system. In terms of optical properties, the Cu-doped heterojunction system containing Ga vacancies introduces deep energy levels leading to the formation of hole-electron complex centres. Compared with the non-magnetic heterojunction system, the magnetic heterojunction system has a higher absorption intensity for visible light, and the red shift of its absorption spectrum is more obvious. In addition, the Cu-doped GaN/ZnS heterojunction system is able to achieve different types of conductivity when containing different vacancy defects.