Spin-polarized exciton formation in Co-doped GaN nanowires

Abstract

Diluted magnetic semiconductors often show a spin-dependent interaction and induced ferromagnetism with high Curie temperature which is a desirable feature to be utilized for magneto-electronic devices. However, the origin of ferromagnetism and optical emission dynamics has not yet been well-understood due to their complicated microstructural and compositional characters. Herein, un-doped and Co-doped GaN nanowires have been synthesized by chemical vapor deposition and the effect of Co dopant on structural, magnetic and optical properties has been investigated. Electron-phonon couple caused by Co dopant, plays a dominant role for enhancement and shift of LO- phonon mode toward higher wavenumber. The incorporation of Co (II) ion in GaN lattice is attributed to the presence of room temperature ferromagnetism which influences their optical properties through exciton-spin interactions. It happens when the Co atom prefers to substitute on Ga sites and induces coupling with neighboring Co atoms to align ferromagnetically, leading to the formation of independent exciton magnetic polarons, as a new elementary excitation that is one of the origins of the bosonic lasing. These findings can pave new way in the future solid-state optoelectronic quantum information technology.