Carbon and zinc delta doping for Schottky barrier enhancement on n-type GaAs

The growth of thin (50–100 Å), C or Zn δ-doped layers on n-type GaAs is shown to yield large enhancements in the effective Schottky barrier height (ΦB) of TiPtAu contacts subsequently deposited on the material. The incorporation of a single C δ-doped layer (p=1.5×1020 cm−3, 50 Å wide) within 100 Å of the surface leads to a barrier height of 0.93 eV, a significant increase over the value for a control sample (0.76 eV). The use of two sequential δ-doped layers leads to an apparent barrier height in excess of the GaAs band gap (ΦB=1.67 eV). This appears to be consistent with the predictions of a unified defect model. Zinc δ doping (p∼3×1018 cm−3) in a similar fashion produces barrier heights of 0.81 eV for one spike and 0.95 eV for two spikes.