The GaAs substrate materials heat treated under several different conditions have been studied by the photoluminescence method. Observations of the 0.37hyphen;eV emission due to Fe2+intrahyphen;center transition show the accumulation of Fe at the nearhyphen;surface region. Secondaryhyphen;ion mass spectrometry indicates that the accumulation of Fe (gsim;1017cmminus;3) is primarily due to the outhyphen;diffusion of unintentionally doped Fe present in the substrate materials. The accumulation of Fe explains the presence of Fe in epitaxial layers and the moderatephyphen;type thermal conversion in heathyphen;treated substrates. Heathyphen;treatment effects on the 1.36hyphen;, 1.40hyphen;, 0.81hyphen;, 0.63hyphen;, and 0.57hyphen;eV bands, respectively, due to Cu, Mn, Cr, O, and Cr are also described.
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