Semiconductor–metal transition in quantum well systems. II

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 View the MathML source, the Hartree–Fock screening function with exchange and correlation effects included pushes the critical well width to a value around View the MathML source. For all other well dimensions the results obtained with the two screening functions are otherwise similar, except for narrow wells View the MathML source 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.