LOW-TEMPERATURE CONDUCTION AND GIANT NEGATIVE MAGNETORESISTANCE IN III-V-BASED DILUTED MAGNETIC SEMICONDUCTOR - (GA,MN)AS GAAS/

We have studied the transport and magnetic properties of Ga1-xMnxAs/Ga As with different Mn content (0.015 < x < 0.071) for temperatures 40 m K-250 K and magnetic fields 0-15 T. Ferromagnetic order was observed i n the samples with.x > 0.02. With incresing Mn concentration, the syst em undergoes an insulator-metal-insulator transition. Low temperature hopping conduction on the insulator side of the metal-insulator bounda ries exhibits giant negative magnetoresistance. (C) 1998 Elsevier Scie nce B.V. All rights reserved.