Iron in heat-treated gallium arsenide

The GaAs substrate materials heat treated under several different conditions have been studied by the photoluminescence method. Observations of the 0.37-eV emission due to Fe2+ intra-center transition show the accumulation of Fe at the near-surface region. Secondary-ion mass spectrometry indicates that the accumulation of Fe (≳1017 cm−3) is primarily due to the out-diffusion of unintentionally doped Fe present in the substrate materials. The accumulation of Fe explains the presence of Fe in epitaxial layers and the moderate p-type thermal conversion in heat-treated substrates. Heat-treatment effects on the 1.36-, 1.40-, 0.81-, 0.63-, and 0.57-eV bands, respectively, due to Cu, Mn, Cr, O, and Cr are also described.