Beyond optical spectroscopy: Isotope effects in hydrogen-related defects revealed by electrical measurements

We investigate isotope effects in hydrogen-related defects in silicon using temperature-dependent capacitance-voltage (C-V) profiling and high-resolution Laplace deep-level transient spectroscopy (Laplace DLTS). Comparison of n-type silicon samples treated with H-plasma and D-plasma under illumination reveals isotope-dependent differences for shallow and deep-level defects in C-V and Laplace DLTS measurements, respectively. C-V measurements show enhanced free carrier concentrations near the surface in both sample types, while the D-plasma-treated samples uniquely exhibit a decrease of the net carrier concentration below 100 K, indicating D-related centres whose charge state changes in this temperature range and which have no counterpart after H treatment. Laplace DLTS measurements demonstrate isotope shifts in the emission rates of the E75′ and E75 defect levels, with ratios e n (D)/e n (H) of 1.8-1.9 measured on the same material, providing direct evidence for hydrogen incorporation into the defect structure. The use of low-doped material enabled the level E75′ to be resolved for the first time. This work extends isotope labeling techniques from optical to electrical spectroscopy, establishing Laplace DLTS and C-V profiling as complementary tools for hydrogen-related defect identification.