EPR evidence for As interstitial-related defects in semi-insulating GaAs

We report the analysis of the residual paramagnetic structure appearing in semi-insulating GaAs after microwave saturation of the ${\mathrm{As}}_{\mathrm{Ga}}$-related spectrum and most intense after preliminary plastic deformation of the material. It is separable into two similar and correlated central hyperfine partially resolved spectra of trigonal symmetry, both attributed to As interstitial-related defects. Some possibilities of suitable complexes, especially in the recent context of the EL2 identification with an ${\mathrm{As}}_{\mathrm{Ga}}^{+}$-${\mathrm{As}}_{\mathit{i}}$ pair, are discussed.