Magnetism and metal-insulator transition in III-V based diluted magnetic semiconductors

We report experiments on the magnetism and the transport in III-V based diluted magnetic semiconductors (Ga,Mn)As and (In,Mn)As. Heat treatment (annealing) at comparatively low temperatures (slightly above the growth th temperature) is unexpectedly found to be effective to improve the ferromagnetism and the metallic conduction. IR optical conductivity measurements and soft X-ray absorption spectroscopy reveal that the double exchange model is a convenient picture to describe the ferromagnetism. The transport in the vicinity of metal-insulator critical point was studied in detail by using the low-temperature annealing method. (C) 2001 Elsevier Science B.V. All rights reserved.