Determining the band alignment in semiconductor/semiconductor hetero-junctions is important for understanding and improving the performance of semiconductor devices such as lasers, photovoltaic cells, and transistors. The band edge positions of the two separate materials may be considered as a zero-order approximation for the band alignment at an interface. The bonding configuration and orientation between the two materials and the presence of an interface dipole, as well as the presence of defects can lead to significant differences. This may explain some of the variation between experimentally reported values.