Electrical characteristics of Au/n-Ge Schottky barrier diode grown on Si substrate

We have grown a Ge layer on Si(100) substrate and fabricated Au/n-Ge Schottky barrier diode. The Ge layer was grown by solid source molecular beam epitaxy (MBE). The growth procedure consisted of epitaxial growth of Ge layer using Sb as a surface-active-agent (surfactant) and high temperature (approx. 620°C) post growth annealing. The crystal structure was evaluated by reflection high-energy electron diffraction (RHEED) and the surface morphology was evaluated by atomic force microscopy (AFM). The RHEED pattern indicated the epitaxial growth of the Ge layer. Examination by AFM revealed some pits on the surface which were considered to be related to dislocation within the sample. The Sb surfactant worked as the donor in the epitaxial layer after the high temperature post growth annealing. The Sb concentration at the surface of the sample was 3 × 1017 cm-3. The fabricated device showed the diode characteristics. The leakage current under the reverse bias condition was high and the ideal factor was large. It would seem that the reasons for the high leakage current and the large ideal factor were related to the pits on the surface of the sample.