Optical and ODMR investigation of anti-site defects in GaP

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Abstract
In p-type GaP:Zn the two luminescence bands at 0.95 and 1.20 eV can be excited with light below the gap energy. They are due to two independent donor-acceptor recombinations. In the 0.95 eV emission the donor is the doublet PP4 anti-site as seen from ODMR. The excitation spectrum of this emission follows the density of valence band states of T2 symmetry with a threshold energy of 1.25 eV. In the 1.2 eV emission the donor is a triplet PP3YP anti-site, the acceptor an impurity with S>1/2 bound to the PP3YP, probably at an interstitial site. A likely acceptor could be Fe3+, which is present as an impurity in the crystal. In the ground state PP3YP is a spin doublet and the proposed acceptor would then be Fe12+. The authors suggest that YP is Ga on a nearest P site (GaP) forming a (PGaGaP) anti-structure pair.