PHOTOLUMINESCENCE EXCITATION SPECTROSCOPY YIELDS BAND-GAP OF GA0.5IN0.5P CONTAINING RELATIVELY ORDERED DOMAINS

Photoluminescence excitation spectroscopy at 9 K reveals that the absorption edge of Ga0.5In0.5P containing relatively ordered domains (grown at 670-degrees-C) is near 1.93 eV, representing the band gap of this inhomogeneous material. Photoluminescence (PL) has been observed at energies lower than this absorption edge energy by up to 70 meV. Along with the unusually slow decay times previously measured, the low energy PL indicates spatially indirect recombination. Therefore PL alone cannot reliably determine the band gap of typical ''ordered'' Ga0.5In0.5P samples. In contrast, the optical properties of relatively randomly ordered (''normal'') Ga0.5In0.5P (grown at 775-degrees-C) are typical of a normal direct III-V semiconductor.