Optically detected magnetic resonance of Si donors inAlxGa1−xAs

Magnetic resonance signals detected both on visible and on infrared luminescence bands from Si-doped ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As samples are described. Most samples show two superimposed resonance signals: a four-line hyperfine pattern and a single line. In this paper we focus on the single-line spectrum, which can be attributed to the Si donor system. The results, particularly the dependence of the g values and the linewidth on the aluminum content of the samples, are explained in terms of effective-mass theory. The resonance is concluded to occur in the donor level ${\mathit{D}}_3$, with mixed X, L, and Γ character in a local symmetry ${\mathit{C}}_2$ or lower. A reduced intensity of the signal in the ${\mathrm{\sigma }}^{\mathrm{-}}$ component of the visible luminescence in heavily doped samples is explained in terms of an anomalous relaxation mechanism.