Lateral homogeneity of Schottky barrier height at metal–germanium interfaces: The role of metal electrodes and interface engineering

We systematically investigated the lateral homogeneity of the Schottky barrier height (ΦB) at metal–germanium (Me–Ge) interfaces, under both Fermi level pinning (FLP) and depinning conditions. Schottky contacts were fabricated by thermal evaporation of four different metals (Al, Ag, Cu, and Au), and ΦB was extracted from current density–voltage (J–V) characteristics based on the thermionic emission model. Due to the FLP effect, all metal electrodes exhibited rectifying behavior with a consistent leakage current density on the order of 0.01 A cm−2. However, Al–nGe contacts exhibited a larger ΦB variation of 17 mV than those of Au, Ag, and Cu contacts. A comparable ΦB variation of 15–20 mV was also observed for Al–pGe contacts after releasing the FLP by O2 annealing. Furthermore, we demonstrated that interface engineering can effectively modulate ΦB homogeneity. Hydrogen annealing prior to Al deposition reduced the ΦB variation from 17 to 6 mV for Al–nGe contacts. These results indicate that the atomic structure at the metal–Ge interface governs the lateral homogeneity of ΦB.