Mechanical stress altered electron gate tunneling current and extraction of conduction band deformation potentials for germanium

Strain altered electron gate tunneling current is measured for germanium (Ge) metal-oxide-semiconductor devices with HfO2 gate dielectric. Uniaxial mechanical stress is applied using four-point wafer bending along [100] and [110] directions to extract both dilation and shear deformation potential constants of Ge. Least-squares fit to the experimental data results in Xi(d) and Xi(u) of -4.3 +/- 0.3 and 16.5 +/- 0.5 eV, respectively, which agree with theoretical calculations. The dominant mechanism for the strain altered electron gate tunneling current is a strain-induced change in the conduction band offset between Ge and HfO2. Tensile stress reduces the offset and increases the gate tunneling current for Ge while the opposite occurs for Si. (C) 2007 American Institute of Physics.