The spin-valve transistor

The spin-valve transistor is a magnetoelectronic device that can be used as a magnetic field sensor. It has a ferromagnet-semiconductor hybrid structure. Using a vacuum metal bonding technique, the spin-valve transistor structure Si/Pt/NiFe/Au/Co/Au/Si is obtained. It employs hot electron transport across the spin valve (NiFe/Au/Co). The hot electrons are injected into the spin valve across the Si/Pt Schottky diode. After traversing across the spin valve these hot electrons are collected across the Au-Si Schottky diode with energy and momentum selection. The output current is found to be extremely sensitive to the spin-dependent scattering of hot electrons in the spin valve. This gives a magnetocurrent above 200% in a few oersted of magnetic field at room temperature. The different physical effects which govern the output current of the device are examined by studying different types of spin-valve transistors that have Si/Au, Si/Pt and Si/Co collector Schottky diodes and Si(100) and Si(111) orientations. It has been observed that along with the Schottky diodes the vacuum metal bonding also plays an important role in determining the output current. In addition, it is realized that collector diodes with extremely low leakage currents, are essential in order to observe huge magnetotransport properties at room temperature.