MnAs/GaAs/MnAs: Morphology and interfacial properties

The properties of epitaxial MnAs/GaAs/MnAs epilayers grown on GaAs(111)B substrates are investigated. The different steps of the growth are detailed from the buffer layer to the top MnAs layer using scanning tunneling microscopy. Despite the high quality of the bottom MnAs surface, uncovered regions of MnAs are observed when the low-temperature-grown GaAs overlayer thickness is 3 nm, while a continuous barrier is formed for an overlayer thickness of 7 nm. The interfacial electronic properties of GaAs/MnAs and MnAs/GaAs are examined with x-ray and ultraviolet photoemission spectroscopy, indicating an absence of detectable reactivity between GaAs and MnAs. Two monolayers of MnAs over GaAs are metallic with a bulk-like valence band. In addition, an n -type barrier height of 0.7 eV is estimated for MnAs/GaAs/MnAs.