Excitons at a single localized center induced by a natural composition modulation in bulk Ga0.5In0.5P

Optical properties of Ga0.5In0.5P grown by gas-source molecular beam epitax y are reported. A strong optical anisotropy due to the spontaneous lateral composition modulation of Ga and In was observed in macro- and micro-photol uminescence (PL) spectra. The micro-PL study revealed that the PL band is c omposed of sharp lines that arise from the radiative decay of excitons trap ped at local potential minima caused by the composition modulation. Anisotr opy in PL rise and decay times was also observed. The detection energy depe ndence of the PL decay time is well explained by considering the relaxation process of excitons from shallow traps to deep traps.