We have measured current–voltage curves and the temperature dependence of the zero bias conductance for ap-type Be-doped GaInP/GaAs heterojunction grown by the molecular beam epitaxy method. We have determined the valence band offset&Dgr;E&ngr;from both measurements and find it to be 310 meV within 5&percent; of accuracy. Similarly, we find for ann-type Si-doped sample that the conduction band offset&Dgr;ECis 95 meV. First-principles calculations have been carried out for the atomic and electronic structures of the interfaces. For the thermodynamically favored interfaces, the valence band offset is found not to be sensitive to atomic relaxations at the interface. The calculated values are in good agreement with the experiments. ©1997 American Institute of Physics.