Interface Engineering and Epitaxial Growth of Single‐Crystalline Aluminum Films on Semiconductors

Abstract Single crystalline aluminum (Al) films are grown on GaAs substrates by molecular beam epitaxy. The high crystalline quality and sharp interfaces of the epitaxial Al films are confirmed by high‐resolution X‐ray diffraction and transmission electron microscopy. Semi‐metallic ErAs is inserted to the Al/GaAs interface to modify the band structure and reduce the optical loss of Al without degrading the crystalline quality. The optical dielectric properties of the Al films are measured by spectroscopic ellipsometry and the optical loss (ε₂) is reduced in a broad spectral region from ultraviolet (UV) to near‐infrared compared to the widely quoted Palik's values. In particular, the loss in the visible region is reduced by a factor of three, indicating the effective energy band engineering by ErAs.