Influence of He-ion irradiation on the characteristics of Pd/n-Si _0.90Ge_0.10/Si Schottky contacts

Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of He-ion irradiated Pd/n-Si₀₉Ge_0.10 Schottky contacts have been measured in the temperature range from 100 to 300 K. Schottky barrier properties such as the Schottky barrier height (Φ_bn) and ideality factor (n) have been studied as a function of temperature. The degree to which their characteristics deviated from the ideal case increased as the temperature decreased. A decrease in Φ_bn and an increase in n with decreasing temperature are observed. Additionally, linear dependence between the so-called temperature factor T₀ and temperature as well as between Φ_bn and n are shown. This type of strong temperature dependence indicates the presence of a large degree of lateral inhomogeneities of the barrier height, resulting from the He-ion irradiation induced defects and traps which produce a variation in the number of free carriers. The presence of electrically active defects introduced by He-ion irradiation at and below the Si_0.90Ge_0.10 surface support this interpretation.