Electric and Magnetic Field Tunable Rectification and Magnetoresistance in FexGe1−x/Ge Heterojunction Diodes

FexGe1−x/Ge amorphous heterojunction diodes with p-FexGe1−x ferromagnetic semiconductor layers are grown on single-crystal Ge substrates of p-type,n-type and intrinsic semiconductors,respectively.The I–V curves of p−Fe_(0.4)Ge_(0.6)/p−Ge diodes only show slight changes with temperature or with magnetic field.For the p-Fe_(0.4)Ge_(0.6)/n−Ge diode,good rectification is maintained at room temperature.More interestingly,the I–V curve of the p−Fe0.4Ge0.6/i-Ge diode can be tuned by the magnetic field,indicating a large positive magnetoresistance.The resistances of the junctions decrease with the increasing temperature,suggesting a typical semiconductor transport behavior.The origin of the positive magnetoresistance is discussed based on the effect of the electric and magnetic field on the energy band structures of the interface.