OPTICALLY DETECTED ELECTRON-NUCLEAR DOUBLE-RESONANCE OF THE S=1 EXCITED-STATE OF THE P-GA Y-P DEFECT IN GAP - THE NEIGHBORING P-31 AND GA-69 AND GA-71 SHELLS

Optical detection of electron-nuclear double resonance (ODENDOR) is us ed to investigate the 1.1-eV photoluminescence of a phosphorus-antisit e-related defect in as-grown p-type GaP. We establish that the observe d ODENDOR spectra arise from the M(S)=0 state of a spin S=1 excited-st ate system in which there are no first-order magnetic hyperfine contri butions. Nevertheless, including higher-order effects via matrix diago nalization, hyperfine interactions are extracted for the central P and several shells of both P and Ga neighbors, confirming that the defect has a P-Ga-Y-P structure, where Y-P denotes an impurity or vacancy at a nearest-neighbor P site. In the case of the Ga neighbors, first-ord er electric quadrupole interactions are present in the M(S)=0 manifold and serve to distinguish the three neighbor shells. The excited-state wave function of the defect is highly localized, essentially all of i t accounted for within the first-nearest P shell. No ODENDOR signals a re observed that can be attributed to Y-P, and its identity remains un determined.