Group III-V ferromagnetic/non-magnetic semiconductor heterojunctions and magnetodiodes

1. A junction device comprising a heterojunction composite comprising a p-type Group III-V ferromagnetic semiconductor component comprising a compound of a formula

(M III 1-x M TM x )M V

and an n-type Group III-V non-magnetic semiconductor component comprising a compound of a formula (M III M V ), wherein M III comprises a Group III metal component, M TM comprises a magnetic transition metal component and M V comprises a Group V metal component, and x is less than about 0.2; a diode coupled to said ferromagnetic semiconductor component and said non-magnetic semiconductor component of a said heterojunction composite; and a voltage source for application of voltage across said device; said device positioned in an applied magnetic field,

whereby magnetoresistance of said heterojunction composite responsive to said applied magnetic field is positive under said magnetic field applied from about parallel to about perpendicular to direction of a current flow through said diode of said device.

2. The device of claim 1 wherein said Group III metal component is selected from Al, Ga and In; said Group V metal component is selected from P, As and Sb; and said transition metal component is selected from Co, Cr, Fe and Mn.

3. The device of claim 2 wherein said ferromagnetic component comprises (In 1-x Mn x )As, and said non-magnetic component comprises InAs.

4. The device of claim 3 wherein x is less than about 0.04.

5. The device of claim 1 wherein said ferromagnetic component is epitaxial to said non-magnetic component.

6. The device of claim 1 selected from magnetoresistive devices.

7. The device of claim 6 comprising a magnetodiode.

8. The device of claim 7 dimensioned to increase current density and magnetoresistance responsive to an applied magnetic field.

9. The device of claim 1 comprising a junction field effect transistor.