Aluminium overlayers on (110) indium phosphide: microscopic aspects of interface formation

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Abstract
The early adsorption and subsequent film growth of aluminium at room temperature on atomically clean cleaved indium phosphide surfaces has been studied using a range of experimental techniques. These include low-energy electron diffraction, Auger electron spectroscopy, as well as core level and valence band angle-resolved photoelectron spectroscopy with conventional and synchrotron sources. The interface formed is complex. For Al coverages below 0.5 monolayer photoemission from occupied InP surface states is significantly influenced following bonding of Al atoms to the surface In and P sites. For larger coverages film growth is believed to involve cluster formation. At the same time the interface shows considerable disorder and exchange reactions occur which lead to the release of indium from the semiconductor. The pinning of the Fermi level at Al-InP interfaces has been studied and the results obtained considered in the light of recent theories of the imperfect interface. The adhesion of Al to InP surfaces has also been briefly studied.