Heterojunctions: Definite breakdown of the electron affinity rule

We performed a simple and straightforward synchrotron-radiation photoemission test of the electron affinity rule, the oldest and most widely used model to predict semiconductor-semiconductor band lineups. The results show, beyond any experimental uncertainty, that the rule is incorrect. The elimination of the rule and of all models related to it considerably simplifies the theoretical situation of this fundamental area of solid-state physics.