The deep double donor PGain GaP

Abstract
The anisotropy of the ligand hyperfine splitting of the PGa4+ antisite ESR signal in GaP has been resolved and analysed. A simple molecular orbital evaluation of the hyperfine data for PGa4+ shows that 92 percent of the density of the second donor electron of the PGa double donor is localised at PGa and its four P ligands. The photoresponse of the PGa4+ ESR signal in semi-insulating and p-type material respectively indicates that the second ionisation energy of PGa is (1.10+or-0.10) eV.