ANOMALOUS TEMPERATURE-DEPENDENCE OF THE HALL-MOBILITY IN UNDOPED BULKGAAS

Undoped liquid encapsulated Czochralski grown GaAs crystals with a tra nsition from semi-insulating to medium-resistivity behavior show unusu al low values of the Hall mobility at 300 K in this transition region. Moreover, in samples of this region an anomalous temperature dependen ce of mu(H) characterized by an increase of mu(H) with increasing temp erature for T<400 K is observed. By model calculations using a standar d effective medium theory it is shown that this anomalous behavior of the Hall mobility is due to the existence of mesoscopic electrical non uniformities connected with the cellular structure of dislocations. (C ) 1997 American Institute of Physics.