MAGNETIC STUDIES OF METAL–INSULATOR TRANSITION IN A QUANTUM WELL SYSTEM

Abstract

Metal–insulator transition in doped semiconductors is investigated in the presence of intense magnetic fields. A variational procedure within the effective mass approximation is employed using the Thomas–Fermi screening function and the exact quasi-Q2D Lindhard dielectric function. The Hubbard model results are justified using an effective mass that depends on interimpurity separation. The nonparabolicity of the subband is included using an energy-dependent effective mass. Though an increase of ionization energy with a magnetic field is observed for isolated donor models, the metallization occurs with an intense magnetic field at a higher concentration for a particular well width. The diamagnetic susceptibility of a hydrogenic donor impurity in GaAs / Ga 1 - x Al x As quantum well systems is discovered in the observation of metal–insulator transition. It is shown that the diamagnetic susceptibility diverges for all critical concentrations for a given well width. The large diamagnetic susceptibility (> 6) is observed at the transition. All the calculations are carried out for infinite and finite barriers, and the results are compared with the existing literature.