Effects of magnetic ions on optical properties: the case of (Ga, Fe)N

Abstract

Because of strong exchange interactions between localized spins and effective mass carriers,transition metal impurities in semiconductors lead to giant magneto-optical effects.Furthermore, band-gap levels derived from open d shells of magnetic impurities act asefficient recombination centers for photo-carriers. This paper reviews studies of excitonicmagneto-reflectivity performed on (Ga, Fe)N epilayers, and shows how hybridizationbetween d levels and band states, particularly strong in nitrides and oxides, renormalizesthe exchange splitting of the valence band states in these systems. Photoluminescencemeasurements on the same structures demonstrate an increase of infrared Fe-relatedemission at the expense of ultraviolet near band-gap luminescence. This sensitivity ofluminescence to the presence of Fe impurities is exploited to monitor the aggregation ofFexN nanocrystals that account for the room temperature ferromagnetism of (Ga, Fe)N, but donot act as inhibitors of excitonic luminescence.