Electron-paramagnetic-resonance study of the Te donor inGa0.70Al0.30As

We report an electron-paramagnetic-resonance (EPR) study of a group-VI donor in ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Al}}_{\mathit{x}}$As (x=0.30). No EPR spectrum associated with the DX ground state could be detected. After photoexcitation with E≥0.6 eV an EPR spectrum is observed, which is attributed to the ${\mathit{A}}_1$(1s) effective-mass state derived from the secondary ${\mathit{X}}_1$ conduction-band minimum. The occupation of this state results from hot-electron capture and is metastable below 40 K. The photoexcitation spectrum of this excited donor state is identical to the photoionization spectrum of the DX ground state previously determined by photocapacitance measurements. The asymmetrical line shape and the absence of the Te hyperfine doublets demonstrate modification of the isolated donor properties by donor-donor interaction.