Structural and photoluminescent properties of low temperature InAs buffer layer grown by MOVPE on GaAs substrates

• Structural properties of InAs buffer layer grown by MOCVD on GaAs at 400 °C were studied.
• Electron transmission microscopy and XRD verify that the GaAs/InAs interface is nearly completely relaxed and that the optimized buffer layer thickness for a subsequent InAs growth at 600 °C is 0.4 μm.
• The buffer layer exhibits n-type conductivity with carrier concentration of ~5×1016 cm−3.
• InAs layer grown at 600 °C on top of 0.4 μm buffer layer is mirror like with sub-nanometer morphology and carrier concentration of ~5×1015 cm−3.

Epitaxial growth of InAs on semi-insulating GaAs was a subject of various attempts to reduce the influence of the ~7% lattice mismatch on the InAs layer properties. The most cost effective and promising method appears to be the growth of low temperature buffer (LTB) InAs layer at ~400 °C followed by a thick InAs layer at ~600 °C. There is a scarcity of available information about the structural properties of the LTB layers, their background conductivity type and level of doping. We have found that a predominant part of the threading dislocations generated at the interface annihilate within the first 400 nm.The average misfit dislocation spacing is 6.15 nm, proving that the LTB InAs/GaAs interface is nearly completely relaxed. XRD measurements have revealed a well pronounced deformation decrease in the LTB layers for thicknesses above 300 nm. The LTB InAs layer is n-type with carrier concentration of the order of 5×1016 cm−3 and can be additionally doped with Te and hence can serve as a bottom contact layer. The morphology of unintentionally doped InAs layer grown at 600 °C upon the LTB shows sub-nanometer flatness and carrier concentration of the order of 5×1015 cm−3.