Abstract
Semiconductor–metal transition in GaAs/GaAlAs quantum well systems with finite barriers is investigated with a more realistic screening function within the effective mass approximation. While the Thomas–Fermi screening function does not admit phase transition below a well width around 60 A ̊ , the Hartree–Fock screening function with exchange and correlation effects included pushes the critical well width to a value around 20 A ̊ . For all other well dimensions the results obtained with the two screening functions are otherwise similar, except for narrow wells (L⩽200 A ̊ ) for which the use of Hartree–Fock function yields values of critical concentration which are one order higher in all the three cases (Q0D, Q1D and Q2D) investigated. In the finite barrier cases when the confining dimension approaches zero (e.g. L→0 in a quantum well) the systems behave as in the bulk due to tunnelling and a phase transition is possible. Our calculations have been performed taking into account Anderson localization and Hubbard model results. Our results support the scaling theory of localization.
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