Mechanism of Blue-Shift of Mn2+ Luminescence in ZnMgS:Mn for Electroluminescent Thin Films

The mechanism of the blue-shift of Mn 2+ luminescence in ZnMgS:Mn is studied. Single crystal zincblende Zn 1- x Mg x S:Mn thin films ( x ≤0.50) were grown by molecular beam epitaxy on GaAs substrates. The photoluminescence (PL) spectrum of Zn 0.50 Mg 0.50 S:Mn peaks at 572 nm, which is 12 nm shorter than the PL peak wavelength of ZnS:Mn. The PL excitation spectrum of Zn 1- x Mg x S:Mn has five excitation bands due to the energy levels of Mn 3d 5 electron configuration. These excitation bands shift to shorter wavelengths with increasing Mg content. The cause of these shifts seems to be a weakening of the crystal field due to an increase in the distance between Mn and S. The ratio of the shift in emission energy to the relative change in lattice constant, Δ E /(Δ a / a ), is found to be 2.3 eV (23 meV/%). This value is approximately half the value of the Mn emission in ZnS:Mn under high pressure.