High-concentration Ce doping at n- and p-type Al/GaAs Schottky barrier interfaces

Al/GaAs Schottky barriers are fabricated with 2.5–20-Å thick doping layers of Ce of concentrations 1020 cm−3 and 1021 cm−3 situated below the GaAs surface. Schottky barrier heights (SBHs) are determined from current- and capacitance-voltage measurements. n-type SBHs decrease with increasing Ce doping layer thickness, while p-type SBHs increase, but to a lesser degree. A cross-sectional image taken by high-resolution transmission electron microscopy shows that Ce is located in the substitutional sites of the doping layers. The changes in the SBHs are attributed to strain induced by Ce atoms in the substitutional sites. The difference in the magnitudes of change observed for n- and p-type SBHs is discussed in relation to the inhomogeneity observed in the density of Ce atoms at the interface regions.