AlSb/InAs heterostructures show promising characteristics for the realisation of very high electron mobility devices. This report focuses on the metamorphic growth of these structures on InP substrate with GaSb and AlSb buffers. We observe poorer lowtemperature electron mobility and room temperature (RT) densities using an AlSb buffer. The photoluminescence (PL) of a GaSb quantum well (QW) grown on the two kinds of buffers suggests that this difference does not result from a larger density of dislocations with an AlSb buffer. The hypothesis of a strain relaxation in the InAs channel on AlSb is also denied since a heterostructure with a thinner InAs QW does not show a higher electron mobility. This leads us to discuss the influence of the roughness of the buffer layer on the temperature mobility and the density of the two-dimensional electron gas. (c) 2007 Elsevier B.V. All rights reserved.