Semiconductor–metal transition in quantum well systems

Semiconductor–metal transition in low dimensional semiconductor systems is investigated within the effective mass approximation. Vanishing of the donor ionization energy as a function of well width in Q2D, Q1D and Q0D systems for different donor concentrations suggest that no transition is possible for very narrow well dimensions (L≤60 Å). The effects of Anderson localization and correlation in the Hubbard model are included in a simple way. Numerical results are provided for the GaAs/GaAlAs systems. Our results show that the critical impurity concentration increases as the dimension is reduced from three to zero. Also the critical concentration is enhanced when a random distribution of impurities is considered. The results are discussed in the light of existing recent literature.