The magnetoresistance of compensated Ge : As at microwave frequencies in the vicinity of the metal-insulator phase transition

The magnetoresistance of heavily doped Ge:As near the metal-insulator phase transition has been studied both on the metal and insulator sides of the t ransition. Measurements were made at microwave frequencies using a nonconta ct technique of electron spin resonance. The field and temperature dependen ces of the magnetoresistance derivative in metallic samples reveal two main features of the phenomenon: a negative magnetoresistance at weak fields, d ue to the weak localization effect, and a positive magnetoresistance at str ong fields, arising from the electron-electron interaction in the diffusion channel. Only a weak negative magnetoresistance with a characteristic low- field behavior is observed in insulating samples. The results are compared with the theory of quantum corrections. (C) 2000 MAIK "Nauka / Interperiodi ca".