Hall effect measurements in undoped In0.5Ga0.5P/GaAs alloy grown by metal organic vapour-phase epitaxy (MOVPE) have been carried out in the temperature range 15-350K. The experimental results are analysed using a two-band model including conduction band transport calculated using an iterative solution of the Boltzmann equation. A good agreement was obtained between theory and experiment. The impurity contents of In0.5Ga0.5P/GaAs alloy, such as donor density ND, acceptor density NA and donor activation energy εD, were also determined.