We report the growth of InSb on GaAs using InAlSb buffers of high interest for magnetic field sensors. We have grown samples by metal-organic chemical vapor deposition consisting of similar to 0.55 mu m thick Insb layers with InAlSb buffers on GaAs substrates with measured electron mobilities of similar to 40000 cm(2)/V s. We have investigated the In1-xAlxSb buffers for compositions x less than or equal to 0.22 and have found that the best results are obtained near x = 0.12 due to the tradeoff of buffer layer band gap and lattice mismatch.