Potential barrier inhomogeneities in irradiated Pd/n-SiGe Schottky diodes

Abstract

Ion implantation, which is an important process in the fabrication of microelectronic devices, is known to have a strong impact on the electrical performance of materials and devices [1]. In this context we study the temperature-dependence of parameters relevant to Pd/Si_0.9Ge_0.1/Si Schottky diodes subjected to He⁺ ion implantation. The irradiated Pd/SiGe junction is linearly graded as evidenced by the capacitance–voltage data but the temperature dependence of the diode’s ideality factor and barrier height is similar to behavior reported for abrupt junctions. The observed trends, usually described as anomalies, can not be fully explained by considering the combined effects of tunneling, recombination, image-force lowering and/or series resistance. It is shown, however, that when taking barrier height non-homogeneity into account the experimental results can be satisfactorily explained. The barrier height is seen to follow a Gaussian distribution with a mean barrier of 0.8 eV and with a standard deviation that appears to be dependent on voltage and also weakly on temperature. It is suggested that the potential barrier deformation itself is temperature dependent at a given bias-voltage with the deformation becoming relatively more pronounced at lower temperatures.