Dual Functionality of a Simple Magnetic/Semiconductor Heterostructure Device: Diode and Magnetoresistive Element

Thin layers of cobalt-polyacrylic acid (Co-PAA) composite with varying weight percentage (wt%) of cobalt in the PAA solution, were prepared by spin-coating on p -Si(001) substrate. The films show large positive magnetoresistance (MR) at low temperature, on application of in-plane and out-of-plane magnetic field. Studies on the transport characteristics of composite/Si(001) heterojunction devices show good rectifying properties like a conventional diode at all temperatures. On application of the in-plane magnetic field, the forward bias current is drastically reduced (unaffected) for all the devices below (above) a characteristic temperature of 50 K. A giant positive MR across the junction of the devices in the order of 10⁵ is observed, which is hardly observed for any heterojunction reported so far. Such a giant change in the MR of a bilayer (magnetic composite/semiconductor) heterojunction device is quite unique and promises dual functionality, working as a diode as well as a magnetoresistive element.