Chemical Mapping of Semiconductor Interfaces at Near-Atomic Resolution

We combine chemical lattice imaging with digital pattern recognition to map, at near-atomic resolution, the compositional change across GaAs/AlGaAs interfaces of the highest optical quality. These maps quantify the information content of each unit cell of the lattice image. Our results show that state-of-the-art GaAs/AlGaAs interfaces contain substantial atomic roughness on scales finer than suggested by optical measurements.