Metal-insulator transition in (Ga, Mn)As

Detailed measurement of transport very close to two metal-insulator critical points in a diluted magnetic semiconductor (Ga, Mn)As is reported. The first metal-insulator transition (MIT) at the dilute-side of the metallic phase is associated with the appearance of the ferromagnetism and the effect of correlation between the electrons (holes) cannot be ignored. On the other hand, the second MIT at higher concentration is purely driven by disorder and disorder-modified Coulomb interaction. It is shown experimentally that the difference in the characters of these two MITs clearly appears in the width of region in which two-parameter scaling works well. This result gives an important suggestion to the long-debated 'exponent puzzle' in the MIT of doped semiconductors. (C) 2002 Published by Elsevier Science Ltd.