PHASE-DIAGRAM OF THE STATES OF THE ELECTRON-SYSTEM OF STRONGLY COMPENSATED SEMICONDUCTORS IN A MAGNETIC-FIELD

Experimental data which shows that the phase diagram of the electron s ystem of compensated semiconductors has a more complex form than the g enerally accepted Shapiro diagram are presented. The magnetic-field de pendence of the conductivity at zero temperature indicates that three successive transitions are possible as the magnetic field increases: ( 1) a metal-insulator transition, which is determined by the positive m agnetoresistance because of electron-electron interaction, (2) an insu lator-metal transition, which manifests itself as a negative magnetore sistance, whose nature has not yet been precisely established, and (3) a metal-insulator transition, which is caused by electron localizatio n on separate donors in the magnetic field. (C) 1996 American Institut e of Physics.