Optical properties of iron doped AlxGa1−xAs alloys

Photocapacitance measurements were used to study the photoionization cross-section spectra of holes in iron doped Alx Ga1−xAs. The spectra are well described by the crystal field theory giving a nearly constant crystal field splitting of about 0.36 eV for all compositions studied. As a result of an extended range of composition (0≤x≤0.76), it was possible to show that the binding energy of the dominant iron center increases linearly with composition and that the relative position of the center is not related to any of the conduction band minima. The variation of the energy for Γ1(5E)→Γ5(5T2) transition in Fe2+(3d6) is discussed for different host crystals.