Magnetic field-induced metal-insulator transition in InP: new result at very low temperatures

Abstract

The metal-insulator transition in compensated n-type indium phosphide, with an impurity concentration just above the critical concentration obtained from the Mott criterion has been induced by a magnetic field. First-order phenomena are considered, corrections to the conductivity due to electron-electron interaction or quantum interferences in the metallic regime will be described elsewhere. Two aspects of the MI transition (Anderson and Mott transitions) are observed by increasing the magnetic field at temperatures down to 50 mK. The Mott minimum metallic conductivity, whose existence has been shown earlier at higher temperatures, is still found down to the lowest attainable temperatures, and its value remains in agreement with the first Mott estimation. For a sample near the MI transition, arguments are given for conduction mechanisms occurring in the impurity band rather than in a tail of the conduction band.