Screening effects inn-type Si inversion layers

The screening of a charged impurity center localized inside the oxide and at the interface of a $n$-type Si(001) inversion layer is considered and its effects on the electron-binding energies have been calculated. The results reported here show that the screening of a point-charge impurity by electrons in a silicon inversion layer can account for the observed electron binding energies of Fowler and Hartstein. It is shown that the linear theory of screening underestimates the electron density around the impurity point charge. The Coulomb potential associated with the impurity located at the interface was obtained for several values of both the screening parameter and the external electric field.