OPTICAL-PROPERTIES OF THE DOMINANT ND CENTER IN GAP

The optical properties of the Nd centers in Nd-doped GaP samples grown by metalorganic chemical vapor deposition have been studied. By using resonant photons to excite the Nd ions directly, we found that the energy separations between the spin-orbit-splitting levels are smaller for Nd in GaP when compared with the corresponding energy separations of Nd in ionic crystals. The crystal field-induced splittings of the dominant Nd center are also found to be smaller compared with the splittings of the other Nd centers in the GaP host. The luminescence lifetime value as a function of sample temperature was also studied. It was found that the luminescence lifetime value of the dominant Nd center remains at a constant 25 mus up to 150 K and becomes smaller as the sample temperature is further increased.