Recent reports of magnetotransport measurements of InSb/Al1-xInxSb quantum well structures at low temperature (3 K) have shown the need for inclusion of a new scattering mechanism not present in traditional transport lifetime models. Observations and analysis of characteristic surface structures using differential interference contrast DIC (Nomarski) optical imaging have extracted representative average grain feature sizes for this surface structure and shown these features to be the limiting low temperature scattering mechanism. We have subsequently modelled the potential profile of these surface structures using Landauer-Büttiker tunnelling calculations and a combination of a Monte-Carlo simulation and Drude model for mobility. This model matches experimentally measured currents and mobilities at low temperatures, giving a range of possible barrier heights and widths, as well modelling the theoretical trend in mobility with temperature.