Effect of impurity distribution on optical properties of Cr-doped ZnSe nanowires: A first-principles study

In this study, we used first-principles calculation methods to investigate the effects of Cr doping at different positions on the electronic and optical properties of ZnSe nanowires. We found that the bandgap of the nanowires is larger than that of the bulk. After doping, it was found that the easiest doping position is on the surface, while all positions require heating for doping. After doping, the change in the intrinsic bandgap was very small, and a large number of defect bands appeared in the middle of the intrinsic bandgap, which are mainly composed of Cr(d) orbital electrons, Se(p) orbital electrons, and d-p hybridized bands. The doping of Cr atoms also affects the distribution of LUMO and HOMO. In the parallel direction of the nanowires, the absorption spectrum exhibits a prominent absorption peak near 0.8 eV, which is caused by transitions between defect bands. Therefore, Cr-doped ZnSe (111) nanowires doped at radius ½ positions are more suitable as mid-infrared laser gain materials.