  We investigate the electronic properties of the (110) cross-sectional surface
of Si-doped GaAs using first-principles techniques. We focus on doping
configurations with an equal concentration of Si impurities in cationic and
anionic sites, such as occurring in a self-compensating doping regime. In
particular we study a bilayer of Si atoms uniformly distributed over two
consecutive (001) atomic layers. The simulated cross-sectional scanning
tunneling microscopy images show a bright signal at negative bias, which is
strongly attenuated when the bias is reversed. This scenario is consistent with
experimental results which had been attributed to hitherto unidentified Si
complexes.
