Metal organic vapor phase epitaxy (MOVPE) grown Ga1−xAlxAs‐GaAs heterostructures have been analyzed by spectroscopic ellipsometry in the 1.6–5.4‐eV region. We show that this technique is capable of a nondestructive analysis of the interface region. The method can distinguish between a physical interface (roughness, alloy clustering) and a chemical one (gradual changes in Al concentration). The results show that extremely sharp interfaces (of the order of one monolayer) can be grown by MOVPE.