The microstructure of spontaneously ordered GaInP₂ alloy

Polarized photoluminescence, photoluminescence excitation, piezomodulated reflectivity, and resonance Raman techniques have been employed to probe the electronic structure of GaInP₂ alloys exhibiting Cu–Pt ordering. The ordering induced band gap reduction and the crystal field splitting of the valence bands have been studied for samples exhibiting various degrees of ordering. Our studies provide evidence for a distribution of order parameters in spontaneously ordered GaInP₂, in contrast to earlier works, which assume that uniformly ordered domains are embedded in a perfectly disordered matrix. Furthermore, the band gap reduction and the crystal field splitting obtained from our experiments are in good agreement with a theoretical model relating these quantities to the long range order parameter in the sample.