The photoluminescence of Ge‐doped AlxGa1−xAs and Sn‐doped GaAs were investigated at 1.4 K. The ionization energy of Ge is strongly dependent on the Al composition in AlGaAs, and is in very poor agreement with the effective mass value. The ionization energy of Sn was found to be 110 meV in contrast with previously reported values. We also report a Sn acceptor bound excitation line at 1.507 eV in Sn‐doped GaAs, and a broad luminescence band peaking at ∼1.5 eV in Ge‐doped AlGaAs.