A novel approach for constructing the band diagrams of semiconductor heterojunctions is discussed and illustrated. It is based on a simple measurement of band discontinuities, Debye length and the width of the space–charge region at the heterojunction interface. Monitoring the changes in the surface potential during heterojunction formation makes it possible to identify the contributions of the interface states and dipole. The approach is illustrated by the results of experiments performed on the InP/In2O3heterojunction. ©1995 American Institute of Physics.