Photoluminescence excitation spectroscopy yields bandgap of Ga_5In_5P containing relatively ordered domains

Ga.5In.5P, ordering, photoluminescence excitation spectroscopy Photoluminescence excitation spectroscopy at 9 K reveals that the absorption edge of Ga.5In.5P containing relatively domains (grown at 6700 C) is near 1.93 eV, representing the bandgap of this inhomogeneous material. Photoluminescence has been observed at energies as much as 70 meV lower than this absorption edge energy. Along with our previous time-resolved photoluminescence results which show unusually slow decay times the low energy photoluminescence indicates spatially indirect recombination. Therefore, photoluminescence alone can not reliably determine the bandgap of typical ordered Ga.5In.5P samples. In contrast, photoluminescence of relatively randomly-ordered (normal) Ga.5In.5P (grown at 7750 C) occurs at the same energy as the absorption edge and exhibits a rapid decay time. These characteristics are typical of a normal direct ill-V semiconductor.