Heat-treated Substrates Research Articles

The behavior of unintentional impurities in Ga0.47 In0.53As grown by MBE

A number of factors contribute to the high n-type background carrier concentration (high 1015 to low 1016 cm−3) measured in MBE Ga0.47In0.53As lattice-matched to InP. The results of this study indicate that the outdiffusion of impurities from InP substrates into GalnAs epitaxial layers can account for as much as two-thirds of the background carrier concentration and can reduce mobilities by as much as 40%. These impurities and/or defects can be gettered at the surfaces of the InP by heat treatment and then removed by polishing. The GalnAs epitaxial layers grown on the heat-treated substrates have significantly improved electrical properties. Hall and SIMS measurements indicate that both donors and acceptors outdiffuse into the epitaxial layers during growth resulting in heavily compensated layers with reduced mobilities. The dominant donor species was identified by SIMS as Si, and the dominant acceptors as Fe, Cr and Mn.

Heat treatment of semi-insulating chromium-doped gallium arsenide substrates with converted surface removed prior to molecular beam expitaxial growth

Silicon-doped gallium arsenide molecular beam epitaxy (MBE) layers were grown on chromium-doped semi-insulating GaAs (Bridgeman grown) heat-treated (converted surface removed before growth) or nonheat-treated substrates. Secondary ion mass spectrometric (SIMS) measurements show a marked reduction of outdiffused manganese in layers grown on heat-treated substrates with converted surface removed prior to MBE growth. Secondary ion mass spectrometric studies and capacitance voltage free-carrier profiling indicate a redistribution of Si in layers grown on nonheated substrates not observed in epilayers on heat-treated substrates (converted surface removed prior to MBE growth).

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.