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Man-made superlattice and quantum wells: past and future

The story leading to the successful introduction of the GaAs/GaAlAs man-made superlattice is probably not known to most. Before I joined IBM and started working under Leo Esaki, I was working and teaching in Texas after I left Bell Labs. My boss, the head of Physics Research at Southwest Research Institute, Frank Witmore, showed me a new book: The Dynamics of Conduction Electrons by A.B. Pippard, Blackie & Son Limited, 1964. He discussed what happens to metals if the mean free path is sufficiently long. For example, electrons move toward the Brillouin zone boundary under the application of an electric field, and are reflected resulting in oscillations.