Two deep (PGa-Cu)-related neutral complex defects in GaP studied with optically detected magnetic resonance

GaP diffused with Cu and Li shows several strong overlapping photoluminescence (PL) bands in the ir midgap energy region, peaking at about 1 eV. In this work two such PL bands are studied in detail, with the aid of optically detected magnetic resonance (ODMR), for temperatures up to 50 K. The two corresponding ODMR spectra are both associated with a triplet (S=1) excited state for an electron-hole pair [bound exciton (BE)] localized at two different complex defects of trigonal symmetry, denoted (${\mathrm{P}}_{\mathrm{Ga}}$-A) and (${\mathrm{P}}_{\mathrm{Ga}}$-B), respectively. Quite detailed ODMR data are obtained, allowing an accurate determination of both g̃, D̃, and à tensors for the BE state. The g̃ tensor is quite isotropic in both cases, close to the value g=2.00, as expected for a BE state composed of a spinlike electron and a spinlike hole. The small residual anisotropy of the g̃ tensor is explained as due to spin-orbit interaction for the bound hole. The D̃ tensor is dominated by electron-hole dipole-dipole interaction, with some contribution from hole spin-orbit interaction for (${\mathrm{P}}_{\mathrm{Ga}}$-B). A central hyperfine (hf) interaction for P is clearly resolved together with an unresolved ligand hf structure on all resonances, typical for the P-${\mathrm{P}}_4$ antisite configuration. The à tensor is slightly anisotropic and has the axial trigonal symmetry, with values about half of the case found for the isolated P-${\mathrm{P}}_4$ donor state. The two defects have quite similar electronic structure and are both suggested to be ${\mathrm{P}}_{\mathrm{Ga}}$-${\mathrm{P}}_4$-${\mathrm{Cu}}_{\mathrm{Ga}}$ substitutional pairs in the two different next-nearest-neighbor configurations along a 〈111〉 axis in GaP.