GaAs surface passivation by ultra-high vacuum deposition of chalcogen atoms

This paper presents a review of the last studies of the GaAs surface passivation by an ultra-high vacuum deposition of chalcogea atoms. The passivation of GaAs(100) surfaces using the chalcogen atoms selenium and sulfur was investigated using high-resolution soft-X-ray photoemission spectroscopy (XPS) at the synchrotron radiation source BESSY in Berlin. Clean homoepitaxial GaAs layers were exposed to selenium or sulfur at elevated temperatures in ultra-high vacuum (UHV) conditions. This chalcogen treatment leads to the formation of gallium sulfide or gallium selenide like layers. The surfaces are terminated with chalcogen dimers and reveal a (2 x 1) reconstruction as indicated by low-energy electron diffraction (LEED). These surfaces were found to be very stable with their reconstruction surviving considerable exposure to atmosphere. In addition, the chalcogen modification leads to a reduction in band bending on the n-type doped samples while the band bending on the p-type doped samples is further increased. (C) 2000 Elsevier Science Ltd. All rights reserved.