Correlation between Crystalline Defects and Electrical Characteristics of In Situ Boron-Doped Epitaxial Si_0.8Ge_0.2 Films

While B-doped epitaxial Si_1–xGe_x films play a crucial role in advanced semiconductor devices, the correlation between crystalline defects and the electrical properties of these films has not been extensively explored. Herein, crystalline defects are intentionally induced by varying the thicknesses of epitaxial p⁺–Si_0.8Ge_0.2 films with different B concentrations on Si. Their effects on electrical characteristics are investigated using unit devices, including p⁺–Si_0.8Ge_0.2/n–Si (p⁺–n) diodes and metal/p⁺–Si_0.8Ge_0.2 contacts. The characteristics of the p⁺–n diodes, including forward and reverse currents, ideality factors, and activation energies, are significantly influenced by the presence of strain-induced defects in the p⁺–Si_0.8Ge_0.2 films. In particular, the ideality factor increases while the activation energy decreases with rising strain energy in the strained films and their subsequent relaxation. This behavior suggests that these parameters are highly sensitive indicators of the impact of crystalline defects in both strained and relaxed films. While the specific contact properties in metal–p⁺ contacts are mainly dependent on the doping concentration in strained p⁺–Si_0.8Ge_0.2 films, they also serve as an effective indicator for identifying crystalline defects in relaxed films.