In this work a detailed study of Si-doped GaAs(0.51)Sb(0.49) grown lattice-matched to InP substrates by molecular beam epitaxy is presented. Electronic characterization using Hall measurements revealed n-type behavior, although with reduced carrier concentrations and mobilities compared to GaAs, ranging from 8.5 x 10(15) to 1.8 x 10(18) cm(-3). Electron mobilities of up to 3120 cm(2)/V s at roomtemperature and 3530 cm(2)/V s at 140 K were determined for the lowest doping levels. The doping efficiency decreased from 52.6% at high doping levels to 13.5% for 8.5 x 10(15) cm(-3). (C) 2010 Elsevier B.V. All rights reserved.