InSb epitaxial layers have been grown on GaAs substrates by low-pressure metalorganic chemical vapor deposition. A 3.15-mum-thick film yielded an x-ray full width at half maximum of 171 arcsec. A Hall mobility of 76 200 cm2/V s at 240 K and a full width at half maximum of 174 arcsec have been measured for a 4.85-mum-thick epilayer. Measured Hall data have shown anomalous behavior. A decrease in Hall mobility with decreasing temperature has been observed and room-temperature Hall mobility has increased with thickness. In order to explain the anomalous Hall data, and the thickness dependence of the measured parameters, the Hall coefficient and Hall mobility have been simulated using a three-layer model including a surface layer, a bulklike layer, and an interface layer with a high density of defects. Theoretical analysis has shown that anomalous behavior can be attributed to donorlike defects caused by the large lattice mismatch and to a surface layer which dominates the transport in the material at low temperatures.