Electrical characterisation of (Ga,Mn,Cr)As thin films grown by molecular beam epitaxy

Abstract We study the transport properties of molecular beam epitaxial Ga 1 - x - y Mn x Cr y As films with x = 3 % and y = 0 , 0.5 and 7%. We find that the hole concentration decreases with increasing Cr content, which can be attributed to increasing hole localisation in the Cr 3 + / Cr 4 + impurity band. Our data indicate that carrier hopping or tunnelling are the main conduction mechanisms in the samples. We find no evidence of ferromagnetic ordering in the films co-doped with Mn and Cr.