interaction in D − centres and quantum dots

A problem of screening of electron–electron interaction by LO phonons is investigated for bound two-electron systems in bulk semiconductors and semiconductor quantum dots. We consider a D − centre and a two-electron quantum dot and obtain the effective LO-phonon-induced interaction between the electrons, i.e., Veff(r12) ∼ e2/[εeff(r12)r12], where r12 is the interelectron distance and εeff(r12) is the effective phonon dielectric function. The calculated phonon dielectric function rapidly increases for small r12 starting from the high-frequency dielectric constant, ε∞, and reaches some constant value, ε̄, at relatively small interelectron distances. We have found that—in most cases— ε ̄ is less than the static dielectric constant, εs. Only in the weakly ionic compounds, like GaAs, ε ̄ εs. We argue that—in the bound few-electron systems—ε ̄ better approximates the average LO-phonon-induced screening than the commonly used εs. We have also shown that the coupling with LO phonons leads to the increase of the binding energy of the two-electron system confined in the quantum dot. 1