Magnetic field dependence of the metal–insulator transition in Ga[Al]As-heterostructures

✍ Scribed by R.D Jäggi; M von Waldkirch; T Heinzel; E Ribeiro; K Ensslin; G Medeiros-Ribeiro; P.M Petroff

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 128 KB
• Volume: 6
• Category: Article
• ISSN: 1386-9477
• DOI: 10.1016/s1386-9477(99)00141-1

✦ Synopsis

A metal-insulator transition at zero magnetic ÿeld is observed in Ga [Al]As-heterostructures where a high density of self-assembled InAs-quantum dots is located in the region of the two-dimensional electron gas (2DEG). This transition occurs only in samples with high dot densities. In contrast to other two-dimensional systems showing a metallic phase the Coulomb energy is comparable to the kinetic energy in our systems. Measurements in perpendicular ÿelds reveal that the resistivity at B = 0 is composed of several contributions. In the metallic regime a weak localization peak is superposed on top of a broad negative magnetoresistivity. In the insulating regime, the weak localization peak at B = 0 develops into a very pronounced negative magnetoresistivity with decreasing electron density. Pronounced, almost B-periodic oscillations in the magnetoresistivity are observed in addition to universal conductance uctuations.