Epitaxial growth of InAs on semi-insulating GaAs was a subject of various attempts to reduce the influence of the similar to 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 similar to 400 degrees C followed by a thick InAs layer at similar to 600 degrees 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 400nm. The average misfit dislocation spacing is 6.15nm, 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 300nm. The LTB InAs layer is n-type with carrier concentration of the order of 5 Chi 10(16) 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 degrees C upon the LTB shows sub-nanometer flatness and carrier concentration of the order of 5 Chi 10(15) cm(- 3). (C) 2014 Elsevier B.V. All rights reserved.