Abstract: The optical absorption spectrum ranging from 200 to 800 nm and fluorescence spectra ranging from 300 to 650 nm of GaP nanoparticles at room temperature were reported. From the optical absorption spectrum it is inferred that the GaP nanoparticles exhibit a direct transition of about 410 nm (3.02 eV) and an indirect transition around 480 nm (2.58 eV). In addition, an absorption peak at about 308 nm (4.02 eV) corresponding to the direct transition at higher energy was observed. The absorption peak was attributed to the transition from the spin-orbit-split valence band to the lowest conduction band along the Λ direction. By observing the fluorescence of the GaP nanoparticles, it follows that multiple emission bands corresponding to the violet, blue, and yellow light are shown peaking at about 400.4−414.1 nm (3.097−2.994 eV), 450.1−466.8 nm (2.755−2.656 eV), and 582.4 nm (2.129 eV), respectively. The violet and blue light emissions are ascribed to the direct and indirect transitions from conduction band to valence band of the GaP nanoparticles. As to the weak yellow emission, it may be attributed to the radiative recombination from defect centers. The spin-orbit-splitting of the GaP nanoparticles is determined as about 100 meV.

Key words: absorption; fluorescence; gallium phosphide; nanoparticles