The influence of a selenium interlayer on the In/GaAs(100) interface formation

The modification of clean GaAs(100) surfaces by in situ deposition of molecular selenium was investigated by synchrotron photoelectron emission spectroscopy. The Se deposition onto GaAs(100) at elevated temperature (330°C) leads to the formation of a Ga2Se3-like layer on the surface exhibiting a (2 × 1) LEED pattern. In addition, the selenium modification induces a reduction in band bending of 0.2 eV on n-doped GaAs while the Fermi level position on p-type GaAs is also shifted by 0.1 eV towards the conduction band. The subsequent In deposition results in a strong reaction of the In with the topmost Se and causes a further shift of the Fermi level of approximately 0.3 eV towards the conduction band for both types of doping. For large In coverages the saturation value for the Fermi level is located 1.25 eV on n-doped and 1.00 eV on p-doped Se modified GaAs(100) above the valence band, which is higher than the value observed for the unmodified In/n-GaAs(100) interfaces (0.75 eV).