Semiconductor crystals provide a larger volume for the presence of self-interstitials compared to densely packed ionic structures. The formation enthalpies of vacancies and self-interstitials in semiconductors exhibit similar values. In the case of silicon, both self-interstitials and vacancies coexist in a state of thermal equilibrium and play significant roles in self-diffusion and solute diffusion processes. Conversely, in germanium, vacancies take precedence in thermal equilibrium and seem to be the sole defect relevant to the diffusion. Semiconductors can possess either neutral point defects or defects in different electronic charge states, as these defects create energy levels within the band-gap of the semiconductor. The neutrality or ionization of a defect is determined by the position of the Fermi level. A considerable dopant concentration significantly influences the diffusion process in semiconductors by utilizing defects with different charge states as carriers for diffusion. At lower temperatures, the impact of doping on diffusion becomes more noticeable as the intrinsic carrier density becomes exponentially suppressed upon lowering the temperature.